I just started using birth control again. I never had any of the side effects listed with birth control all the others times I have taken them. I have never been on the same formulation. I have had unprotected sex three times. The first time I took plan B. The second two times I had just started birth control and he pulled out. About ten days after the first time, I had some spotting. I then started to experience fatigue, nausea, constipation, breast tenderness, migraines, and started bruising easily and craving red meat which I never eat. I have never had problems with bruising before, which I know can start to occur with a lack of enough iron. I took an HPT, it was negative and then I had my period, but it was not like my normal periods. Went to the doctor and had a blood test, which was also negative and I understand my symptoms are similar to side effects of birth control. I am now on my second pack and my symptoms have worsened. Nausea all day, headaches nearly every day, and now I have low back pain, but it doesn't feel like cramps from menstration. Took another HPT and again negative, but I feel like I know my body really well and something is up. I am very active, and am in fact a fitness instructor. I never get sore, but have been lately, and have been feeling muscle pains I have never had before in my chest and quads. A few years back, I was on birth control and was getting extreme night sweats so my doc tested my hormone level, they came back with zero female hormones. He took me off the pill and then retested a month later. Very minimal improvement. I suppose my question is, could I be pregnant even with negative results and having had my period. There are women that have had this happen to them as well.