What could be going on?

I am 34 years old and I normally have a 28 day cycle. I am taking two Antibiotics. I am done with azithromycin but I am still taking the cephalexin. My husband and I was trying to get pregnant until I got the call that I had a STD which means he cheated!! I should of had a close to positive LH test by now. I am having a very light red bleeding which is not normal for me unless I am starting my period! Which is not due right now.