Possibly???

Had sex on the 10th while ovulating. My nipples got darker and more tender. Period was due Sunday (today is Tuesday)but nothing happened until today when I started seeing brown spotting and a clot. Still haven't started bleeding and the brown is starting to fade now. Could I be pregnant?? Going to wait a few more days to take a test but what do you think??

UPDATE: Woke up this morning and had a big clot of regular blood so I thought everything was fine. But a couple hours later I went to change my pad and there was nothing but a little brown like before. Wtf is this?