Bleeding after sex

I am in the implanon birth control and I'm pretty sure my 3 years is over. I use to get my period ever few months but now I think it's irregular. My last period was 11 days and after that I had sex "which was last night" and today I have been spotting... This also happened the last time I had sex and I spotted for a few days and I lost track of it  and it seemed like I started my period again shortly.