4weeks and 3 days and bleeding

My husband and I had sex yesterday and about an hour later I started bleeding a little. Woke up this morning to a ton of blood. I have had cramps in my lower back for almost a week now. They aren’t as strong as period cramps. Although last night they seemed a little stronger. I have had over 8 pregnancy test that are positive over the last week. Three different brands. I had a chemical a few months ago. Could all the bleeding be from sex? Or am I having a miscarriage?