Implantation bleeding

I've been on blisovi fe (BC pill) for 3 months and still haven't had a period. Last pregnancy test was a few weeks ago and was negative. I started Keflex (antibiotic) last Friday and am taking 2,000mg everyday. My boyfriend came in me 3 days ago (we forgot about needing to use a backup method while on antibiotics) and I've had cramps for 2 days. Today I had very very light pinkish brown discharge which I've never had. Could I be ovulating or having implantation bleeding? It seems too early to have implantation bleeding if I had somehow ovulated. What do you think?