Hello, some antibiotics & not all, can interrupt with the action of oral contraceptive pills (OCP). Antibiotics like Tetracyclines & Ampicillin suppress the intestinal flora responsible for the re circulation of OCPs thereby reducing their level. This inhibits the efficiency of OCPs resulting in their failure. Nausea of morning sickness can occur as early as 2 weeks after conception. This is due to early increase in the levels of estrogen & progesterone. Dizziness tenderness of breast & mood swings occur within the first week of pregnancy in many women. But fluttering is usually felt only around 4 to 5 months (24weeks). Bloated abdomen, nausea & lower abdominal pain are also found in persons suffering from urinary tract infection. Severe nausea, reflux, abdominal pain, dizziness could also be due to gastritis caused by antibiotics. But both conditions (UTI, gastritis) will not result in breast pain. It is always advisible to follow some other methods of contraception (like condoms) along with OCPs Whenever the need to take antibiotics arises. Since the possibility of pregnancy due to failure of oral contraceptives is there, do pregnancy test to rule out conception.