Why Am I Missing My Period?

Hi, I'm on birth control, the pill, and l past month I missed my period. I haven't been taking my pill everyday, I accidentally missed a few. I took a test the week that I missed my period and it was negative. I took another test the following week and it was also negative. This month I've noticed that every time me and my husband have sex "doggy style" I end up vaginally farting when were done, this has never happened before. It has been exactly a month since my last missed period and I have yet to get my period this month. Do you think I could be pregnant?