implantation bleeding or not?

My husband and I have kind of stopped trying. We still have a lot of sex just stopped tracking ovulation due to a lot going on in our lives. Last week I had some very light pink discharge after I peed and after sex I mean it was so light you could barely see it. This Sunday after sex I noticed the same thing some pink and the smallest amount of blood. I put a pad on and never switched it during the day (very little on pad). I know it's not my period because I do have heavy periods. I've had a little bit of cramps for a day or 2. But no other symptoms of my period. Could it be implantation bleeding? I took a pregnancy test yesterday and it was negative.