I was prescribed Sulfamethoxazole and im suppose to be taken for 3 months. After a month on it I suspected I was pregnant and quit taking the prescription. This has been a month ago. I am approx. 2 weeks late for my period. I have had a child before and have experienced a lot of strange symptoms that I had while I was pregnant before. I only weigh about 115 pds and im suddenly and rapidly getting bigger in my lower stomach/ uterus area. I didnt have any difficulties in my first trimester like this with my first child. For the last 2-3 weeks I have taken probably 5-6 pregnancy tests and they have all been false... Is it possible that this prescription is causing me to get a false negative test result?