I am 31 with two boys ages 14 and 11. i recently just had unprotected sex and then started my period the day after. My period lasted the normal 4 days but after the 4th day I woke up very nauseated and have been nauseated ever since. I'm also taking an antibiotic bactrim DS 800mg but have been taking it 5 days before getting seriously nauseated. Could I be pregnant? Please help me!