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.
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
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.
Nothing wrong with masterbation and never heard of any long term side effects. Its natural