mid cycle bleeding

so I had some mid cycle bleeding around the 8th till the 10th of this month. I think it was brought on by stress... we'll me and my hubby got some a couple days after and his pull out game wasn't to strong that night which was probably around the 12th. I was supposed to start my period on the 20th and didn't I've takes 2 pregnancy tests which are negative but I'm having dull cramps and lots of discharge and headaches. could I be pregnant and be showing symptoms but a test still.wont read it?