Over 2 Weeks Late...

I am officaly 16 days late. I have taken 4 tests all negative. I have never been pregnant so I'm not sure how I'm suppose to feel (I have read about all the symptoms though). I was experiencing headaches for about a week. I went to my allergy doctor and she said I had the beginnings of a sinius infection. Those headaches has since went away. My lower back was hurting that same week but that has since went away as well. For the past 2 days I have been having period like cramps and I keep thinking my period is coming, but nothing yet. I'm so tired of spending money on pregnancy test!! Everyone asks me how come my husband and I aren't pregnant yet and I always say I don't want kids because it wouold hurt me to bad to say that I've been trying with no success. I feel like a huge failure! So many people I know end up pregnant by mistake and when you are a teen all you worry about is getting pregnant but for some of us when you actually try you get nothing. I'm so discouraged. I feel like my normal self besided these cramps so I really don't think im preggers once again. I'm not sure how to cope with this disappointment over and over again. I even tell my husband that I don't care about having kids because I can't even admit it to him how much I want a little bright eyed person that looks likes us.