TMI something weird happened

On day 9 of my new cycle I had sex. We usually do it a lot of times in one night. At least 5 times. Then I seen my babe again and this is day 19 which was this last Friday/Saturday. We start having sex and after we finished I felt I had to go to bathroom to wipe off. As I’m wiping I looked on tissue and it was blood! I ended my period on day 7 of the cycle and I usually have a 40 day cycle average. So I told my man this is really weird to be spotting. The sex wasnt any more rough or any thing. In fact I cummed two times in a row. So I’m wondering what the heck! Why was I bleeding. We then did it a bunch more times and I continued to spot threw out the night. And the whole time this app is saying I’m in my fertile window. I think I was actually ovulating according to the app. I spotted the next but very lightly. So Sunday and today no more spotting. So what the heck! Can some one give me some insight on this please? Should I go crazy yet? I also have been taking prenatal vitamins for about three months now.