Weird discharge after withdrawal bleed?

I’ve been on my same pill for 1.5 years with no problems. As of recently I get spotting between period and after my bleed I get ALOT of yellow/clear discharge that seems to have a light green tint on toilet paper but just yellow/white on my finger. No burning or itching or bad smell. I was already tested for STDS last year while with my current boyfriend. What could be causing this???