Bleeding

I’ve been on nexplanon since March so 6 months, I had irregular bleeding until June. I was away from my boyfriend for the whole of July however when I did see him a month later and we had sex, I started bleeding again and it’s been like a period. Then it started to slow down but then we had sex on Thursday again and i started bleeding red and like a period again. Is this irregular period from the nexplanon… has anyone experienced bleeding after sex? I’m so confused I feel like the sex stimulated my period maybe? Apart from that I’ve not been feeling anything else at all.