Period after a chemical pregnancy?

Hi everyone,

So I missed my period on 26th of August and tested positive for pregnancy. I kept taking tests till about 2nd of September and all positive but the lines didn't get any darker. On 7th, I started spotting. On 10th, when the bleeding got heavy I went to ER. They did urine test and I tested negative. They told me it was period blood. I'm guessing may be I miscarried way before 7th and didn't realize. They told me I can ttc anytime I want.

Anyway, I bled till 15th and I thought I was done with period. Then I had sex on 17th and started having my period again on 18th. It's been 2 days and I'm still on my period.

Does anyone has any idea if it's normal? Has anyone experienced anything similar? If yes how long did you bleed for? How do I calculate my ovulation this month?