Early Pregnancy Signs.. Sex Hurts

Hi everyone, I ovulated on the 4th Feb and had sex a couple of days before and two days after. Since Monday I've experienced some slight bleeding, nothing that needs a liner. On Monday it was just a tiny bit on a tissue but yesterday I had sex with my boyfriend and I'm sorry if it sounds gross but when I went to the bathroom quite a lot of brownish discharge was mixed with his cum. My stomach has cramps and it kinda hurt to have sex with him and today my stomach had this pulling feeling with cramps too. 
I've taken a pregnancy test today but it was negative. I'm worried there is something wrong with me, I've not had an early period before and this doesn't feel like a period. Just before I ovulated I had a Hysterosalpingogram which found my tubes were blocked and by increasing the pressure of the liquid they became unblocked. I'm worried that this strange bleeding may be a complication of that.