LADIES PLEASE HELP ME/POSSIBLY MISCARRYING

I have an IUD, went to check the strings friday and they weren’t there. Took a test - positive. Took 10 in total over the weekend from Friday - Monday… all positive. I had spotting Saturday around noon and though the rest of the day. Started bleeding sunday but never enough for a pad or tampon, just brighter blood when i wiped. Still bleeding a little bit and had OB appt yesterday to check for IUD - not there, they think it fell out. No sac on ultrasound either, doc tested urine, it was negative. She wanted to draw blood just to be sure and i got my results this morning - 24 mIU/mL. I know that’s a grey area, but the results put me around 3 weeks. I don’t know if this is a chemical since i’m bleeding a bit, or if I tested way too early and my tests were all sensitive and maybe the office’s aren’t as sensitive and i’m just super early? I thought the sensitivity was the same. I’m just freaking out, anyone been through this or have any thoughts? TIA

Edit: I’ve had a rocky history with birth control. Nexplanon - bled the whole time with terrible migraines, combo pill - awful pms, mini pill - pregnant with my son, Nuvaring - gave me a pulmonary embolism (blood clot in the lungs), and Mirena #1 fell out in the shower. Never felt it come out, but felt the string tickle my leg and it literally fell out. My uterus is also tilted back, so they said that can give IUD a little more access to come out, but since my last one came out on its own they think this one has as well. They checked all in my abdomen and back during the U/S yesterday and couldn’t find it.

*I had Mirena IUD both times, and the doctor has not called me yet to discuss. She said if numbers were elevated, we’d retest. If not, she wasn’t going to worry about it.

Update: I don’t know if anyone will see this, but for those wondering.. I had my labs repeated yesterday at my hcg was at 16, so I’m having an early miscarriage/chemical pregnancy… I have to go back in a week to check my levels and make sure they’re close to 0. Praying for all of you mamas who have been through this/are experiencing symptoms of miscarriage, my heart is with you. 🤍