The deal with masturbation is that it is pretty great! It is a sexual activity that is entirely under your own control. You don’t have to focus on what the other person (or persons) with whom you are getting it needs at the same time; it is totally your thing. It’s also great because you don’t have to worry about STBBIs transmission (because you aren’t going to infect yourself by yourself… except if you use some sex toys that another person had used very recently) and there is no risk of pregnancy.
As for whether or not it’s good for your health, I am not a medical expert so I can’t give you statistics on exactly what masturbating does in terms of the actual biochemistry of your body, but I can tell you that it can help release pent up stress and/or sexual energy, which is definitely a good thing. It can also help you relax and maybe get sex off your brain for a moment. There is no set number of times you can or cannot masturbate in a week. Some people masturbate several times a day, some several times a week, and some never. As long as what you are doing feels good to you, is not causing you any pain, and is not interfering with other things you need to be doing, there should really be no reason why you cannot masturbate when you feel like doing so.
Hope that helps!