Bfp, period still bfp

Cassie

Hoping someone has some advice. Apologies for the long post. I’m just wondering how long it would take for hcg to fall? I got a Bfp the day before AF was due, then started bleeding the day after AF was due (was heavy like a period) fast forward to a couple days later I’m still getting bfps and even got pregnant on a digital. I have quite a lot of lower back pain but the doctor has said wait until Friday and keep testing. I’m just hoping someone has been through a similar situation and maybe has some advice. Thanks ladies