after I masturbate, I get a 20 minute pain in my penis after I ejaculate. I am 17 years old, never had sex and diagnosed with MS (Multiple Sclerosis) I started getting this pain about four days ago when I masturbated for the first time in about two weeks. I normally masturbate 1-2 times a day and I get no pain whats so ever. When I masturbated four days ago and two days after that I would get some sort of sting/burn pain which lasts for 20 mins, the 20 minute pain was annoying but didn't make me what to cry but when I masturbated today to see if the pain was gone, the pain was still there but it wasn't as bad as before and it felt like it was easier to ignore, so hopefully thats a sign of recovery? I don't think its an infection because I have no blood in the urine and semen, no discharge, it doesn't hurt when I pee and my pee is clear. I would like to add that lately I have been drinking quite a lot of fizzy drinks and before I masturbated in the first time in four weeks, I have been giving my self "forced" erections and teasing my penis by rubbing it and making a little bit of semen come out, then I would do it again. So what could it be? Do I need to take it easy? Should I let my penis have a resting period or is it an infection? I am concerned about this because this kind of thing has never happened to before.