Missed period and 6 negative tests. What else could cause a missed period?

[am2013]

I am 21 years old and I have had a missed period. Like most women, I get signs of my period coming. I had small pains like I usually get and they only lasted a few minutes. The pains usually get sorer when my period is near but not this time. The small pains stopped over a week ago. I have had no pain or anything since then. No sign of period. I went to the doctor during the week and I done a doctors urine test. It was negative. She said to wait another 2 weeks and test again. She said it is very easy to get pregnant, but my boyfriend and I are always careful. We use condoms and my boyfriend always holds the base of condom when pulling it out after. I haven't really had any signs of pregnancy. My next period is due very soon. I just want to know what else could be causing this missed period? It a pain in the arse and is really worrying me and my boyfriend. I am slightly over weight and I try to exercise if that matters. Thanks!

[am2013]

Thanks very much for your advice. By the way i am nearly a month late and home pregnancy test is still saying negative. What are the chances i am pregnant?

[kaitymomma2013]

Condoms aren't 100% affective. Only thing thats 100% is abstinence. I suggest wait two weeks and get a blood test done. If it comes up negative again id ask your doc why you have missed cycle. Other things it could be stress, just a missed cycle happens for some women, infection. It could be almost anything. It could even be your body showing symptoms of pregnancy because your so worried about it. I suggest just not worry. If you miss your cycle again get a blood test. They are more accurate.