light period?

So I had sex on Friday for the first time since September. We used protection but he did cum on me and some got on my thighs but none of it touched my vagina. I was supposed to get my period 2 days after I had sex and I did but it's a lot lighter than normal. I was just wondering if that was normal because I had sex or not. My period is already really light because of my bc but now it's almost non exsistent.. is that normal?