Hcg drop then rise!

I found out at 6wks I had what seemed like ectopic pregnancy in my left tube but it hadn’t been confirmed before my hcg started dropping 4000 to 1980 then 800 I was also bleeding and passing clots and stuff so it seemed like I was miscarrying naturally and didn’t need intervention. Let last night I stated bleeding and cramping again so we did blood work and my hcg has risen to almost 1300….. I have an ultrasound tomorrow to check for retained tissue. Anybody have experience with this