infertility

Hi there! 
Fair warning: This is long. But I could really use the help. Thank you.
Also I don't know which category this would go under so I'm going to put it under a few of them. 
I'm having some trouble. So let's start from the beginning. My husband (boyfriend at the time) were beginning to be sexually active. I was on the pill at the time. At this point I have been on the pill for about 8 months. Then a few months after our wedding we decided we wanted to try and have kids. So I had stopped taking the pill and we had heard from many people and read that you should start trying to conceive three months after ending birth control. So 6 months goes by and still nothing. When we kept trying and constantly being disappointed we ended up making a doctors appointment with my OB/GYN. With that appointment I was asked multiple questions and a few tests done. My doctor had given me the whole speech on how there are multiple tests that can be done and which one she recommends. So we ended up doing two tests. I had gotten a blood test and an endometrial biopsy. With the tests my doctor had ended up telling me I was infertile. I asked why and she had told me that there was no reason known for this. I couldn't understand how this was possible. How I could be infertile at such a young age (18) and how there could be an unknown reason for it. She had just told me  it's called unexplained infertility and then proceeded to apologize and tell how there is treatment available. Which at this point I was doubting everything from that point on. How could there be a treatment for an "unexplained infertility"? Just didn't make sense. So I just kind of ignored the fact that I was infertile and went about my life. A couple of months go by and my husbands sister (17) announces she's pregnant. This just rushed me back and threw me for a loop. All these ladies are getting pregnant I just can't. So I kind of snapped one day when she was saying she wishes she wasn't pregnant at this age. That just made me irritated and sensitive. Needless to say that's the day my husbands family found out I was infertile. So a week goes by it's not September 23rd I was just thinking I'm only 4 days late for my period. It's now October 5th and I still haven't gotten my period. So today I went out and bought about 16 pregnancy tests, yes 16. I bought two different brands, clear blue and first response. I took 12 tests and every single one them came out negative. So now I'm trying to figure out why I'm having these terrible cramps like I'm on my period but I don't have my period. So why these pains when I don't have my period? Why did I not get my period last month? Someone help me please. Being 18 years old and finding out you're infertile for an unknown reason is devastating and I really just need an answer instead of everything being unknown.