Spotting after period

This is the first time that this happens to me... My period started 03/10 and ended 03/15  I had sex two days after it finished 03/17 and I started bleeding a little bit, it was like a heavy spotting plus a little clot it lasted like an hour..yesterday I bought clotrimazol 2% for yeast infection because I had a burning sensation only inside my vagina (I don't have a UTI) and today cycle day 10 I wiped and I'm spotting again but only like drops it looks like light pink.. Why is this happening to me? I'm pretty sure I don't have any STD'S so please don't tell me to go get tested ! What else can it be?  I have a regular period also my fertile window stars in two days.