Am I ok?

I miscarried at 6 weeks starting January 26th. I bled moderately heavy for a 6days-week. I had sex on the 3rd and for about 4 days I’ve had this brown mucus (usually only when wiping) (TMI) there was more but today it’s basically gone. I thought it was my period returning but nope. My last hcg reading went from 99 to 74 in a day or so. I also had an ultrasound on Monday and it showed something 3mm but they didn’t know what it was but she said it can’t be a baby. Do I have an infection? Or what are your thoughts?

Ok