Nothing wrong with masterbation and never heard of any long term side effects. Its natural
Masturbation is a natural habit. If you do it naturally i.e when there is a natural urge (not excited with porno), you will be ok when you are with your partner.A person addicted to porno, will face a lot of problems when he encounters real situation.
Masterbation can become a serious problem if it gets out of hand especially associated with porn. And once you get addicted to porn it becomes like an addiction ex drugs, alcohol
I'm in the same boat!
I'm 18 and I started masturbating when I was about 15. I do it everytime I take a shower. Sometimes I take 2-3 showers a day JUST to masturbate.