Thanks for your question – it is extremely relevant to most teenage boys and young men regardless of sexual orientation. Un-provoked and frequent erections are something that is very common in young pre-teen and teenage boys; usually uncontrolled erection start around age 11 and can last well through the teenage years.
An erection is only dangerous when the penis stays or is provoked artificially like with drugs such as Viagra, to stay fully erect more than 2-3 hours. If you do stay erect or your penis hurts while being erect than it would be important to see a doctor.
Priapism is a condition where the blood does not drain properly from the penis. Since an erect penis is filled with blood vessels that fill with blood (arteries open and the veins leaving the penis constricted, creating pressure) It is normal to go hard and go soft in cycles, many times over a few hours, even when having sexual relations. Often boys and men will go soft quite soon after climaxing (with pre-ejaculate and/or ejaculate) and in young teen boys there's a period where the penis gets erect and the boys can climax, but with no ejaculate or semen.
About the penis http://health.howstuffworks.com/sexual-health/sexual-dysfunction/viagra1.htm
I noticed in this question that you are 18 and you are still are getting frequent uncontrolled erections. It may be that you started getting erections, thinking about sex, masturbating and being sexually active a little later than other boys. I do not think there is anything to worry about because sexual maturation is not fixed by age, just like growth spurts in teenagers can appear before age 25, but they vary from boy to boy.
Just to confirm that masturbation and fantasization is a normal part of growing-up, trying to repress your sexuality makes you even more vulnerable to unwanted erections. Thinking or being embarrassed by erections may make them worse; it causes a trigger in the brain. Most unwanted erections are psychologicaly based stimulation, in other words they come from your brain. Your brain may be triggered even by something non-sexual because as sexual maturation happens Testosterone is rushing through the body, preparing you for reproduction. I have read a situation where one teen enjoyed pleasuring himself with food.. so every time he went to the supermarket to help his mom with groceries, he would get erections when looking at or touching certain food items like cucumbers, carrots, bananas, melons, apple pie (that last idea comes from the movie American Pie)
More things like thoughts, fantasies, wet dreams and sexual tension get your brain sending signals for you to become errect sometimes at the most inappropriate moments like in the middle of class as you have to stand up to give a presentation or in gym class lookerrooms as you’re changing. There are things around you that could also cause this, like seeying other people naked, getting undressed or showering with others, or having to wrestle with or spot a teammate you find attractive, also seing other people being intimate in public, holding, hugging, kissing or heavy petting, even if you are gay and see heterosexuals. Of course pornographic images or videos are major stimulants!
Apart from psychologicaly based stimulation there’s physical stimulation wearing certain kinds of clothing, sports gear or doing activities where you move a lot, running, bicycle, motorcycle, horseback, heavy vibration like in a roller coaster, etc. can all provoke erections because there is movement and rubbing. You may also look at the type of underwear and clothes you wear, some boxers or underwear because of the way they are made may be stimulating you as you sit, walk or run. Also certain types of shorts, jeans or other clothing whether they are tight or loose may be rubbing on your genitals in erogenous zones, this may also be helping to cause the problem.
Masturbating is a good way to desensitize yourself a bit, although when boys start masturbating it does the opposite for the first few months there are frequent erections. If you get bored or find you’re not getting excited enough while masturbating you may want to try advanced masturbation techniques, just Google it, there are a lot of suggestions on the web. In guys who have cut (circumcised) penises masturbation is simple, guys who are uncut (where the head of penis is usually very sensitive because it is protected by foreskin), what is suggested is to retract foreskin when masturbating to stimulate the penis head, this will help in desensitizing yourself.
A lot of teens ask: am I masturbating too much?, the answer in general is no. The negative part of masturbating is that you are rubbing sometimes quite vigorously skin that is quite thin – genitals are fragile compared to the skin at the bottom of our feet, for example. So irritation, redness and in bad cases, bleeding and infections could happen. To avoid this you should ALWAYS wash hands thoroughly before you masturbate, also using lubrication is recommended especially for those who need to masturbate a lot before climaxing. Personal lubricant can be found at most pharmacies and at all sex shops, it's better you buy a condom-safe water-based lubricant so you will have it on hand if you happen to have sex with a partner. Oh and at the same time pick up a box of your favorite condoms, it's time to put those everywhere, like in your locker at school, in your school bag and at home. If you have a car, leave a few there too, hide them in a cool dark place preferably in a rigid container so the condom is not exposed to heat or folded or squeezed, which is bad for the rubber latex.
Sex can and does happen in any place at any time, so it is better you have them ready! Because having unprotected sex whether gay or straight is irresponsible, doing so puts your life and that of your sexual partner at risk. The Human Papilloma Virus and the HIV virus kill thousands of people each year around the world, especially in developing and over populated countries and in the case of HIV the rest of the infected, like here in North America are left having to take strong and expensive medications for the rest of their lives. Getting infected is PERMANENT even if sex only sometimes lasts 5 minutes!!!
As you learn more and more about your body and your personal sexuality, what turns you on, what you fantasize about, masturbation techniques and when you are ready, being sexually active with the males or females you enjoy being with, all these will help your brain to learn when it's the right time to get erect.
JP for the Alterheros team.