I am 18 years old and have never had a period. My OB/GYN that I saw when I was 16 told me it was just because I was skinny and ran all the time even though I'd had one period when I was 14 that lasted 5 days and then I never had it again. What she didn't know though, is that shortly after my visit, I started having dark brown discharge and sometimes white. I then had sex for the first time when I was 16 and was worried of how I would know if I were pregnant or not because I don't have a period to be late... but then I realized that by not having a period, I'm unable to get pregnant because my body's not ready to have a child. Is this a correct assumption??? Also, recently I had sex again after 3 to 4 months of not having sex and I quickly became sore and it was very hard for him to get inside me due to me being so sore and raw. It was like there was a lot of friction going on. I stuck through it though and he used a condom and everything went fine. But then the next day we did it again and I was soo incredibly sore. It hurt but once again I stuck through it because I wanted to finish what I started. Then, the next day my vagina was very itchy and sore and hurt. It wasn't swollen or red or anything though.

What's wrong with me?
Why haven't I started my period yet?
Why do I have brown discharge?
Why am I itching?
Why am I sore during intercourse?

Please help. I want to get a guess on what's wrong with me before I go see an OB/GYN.