Why did I bleed?

I had my period two weeks ago and according to this app my ovulation period ended two days ago . Last night while having sex with my boyfriend I was bleeding and it happened all three times(🙈). It looked like old blood at first then started looking regular with no strong scent or even cramps or anything like that. Just a little sore legs from the sex. I don’t have it anymore but I’m confused. We had sex two months ago btw so it’s been a while (long distance) .

It wasn’t a lot of blood either just tiny bits. When I took a shower and tried to wash myself off cm came out with bits of blood in it.