LOL, you and your womb!

I'm afraid the only way to be completely sure of what is happening is to use a reliable barrier method of contracption (i.e. a condom) or (EVEN BETTER) abstinence for 16 days from the last time you DTD and then do a test (because the vast majority of pregnancies will show up by the 16th day after the act). If it's negative then you're not PG and can go on the minipill (which BTW made me not bleed for 54 days then bleed continuously for the following 23 days, JIC you were looking for menstrual stability!).

Best of luck hun

Bx