Is pregnancy unlikely?

I've been on birth control for 2 years. I almost always take it on time sometimes several hours after the 4 leeway but not often at all.. I might of completely forgot for one day out of the month. My boyfriend and I have sex on a semi daily basis and never use protection, he always ejaculates inside. I thought I might of been pregnant, because my breasts were very sensitive and sore to the touch and I was urinating frequently, every 30 minutes or so. so I took a test about 2 weeks prior to my period and it came back negative. About a week after that my period started and I bled very heavily and had some clotting and beforehand I was having bad back pain. After the heavy bleeding when it started my period was light and ended in about 4-5 days. I thought this was a miscarriage but I'm not sure. It's been two weeks since that happened, I always have some lower back pain but for the the past 8-9 days it's been more frequent, I've been getting headaches more frequently. When I wake up everyday for the past week I've felt very nauseous like I'm going to throw up. This is accompanied by headaches but not every time. I'm also having alot of discharge, which is whiteish and doesn't have a strong odor at all. I recently had a pap smear and other testing done so I know it's not related to any kind of infection or STD. I've had to get larger size bras because my old ones weren't covering everything they were supposed to.. I attributed this to the dryer. Only a slightly larger size tho. I've been falling asleep just watching TV which isn't normal and just alot faster in general. I've been aggravated very easily and rather bitchy (or so I've been told) and cried over some things that usually wouldn't upset me. My eating habits haven't changed really. please let me know your opinions on whether or not this could be the signs of me being pregnant what I think was probably a miscarriage made me believe I definitely wasn't since I also had a semi normal period. thanks :-)