Miscarriage and Pregnant before next cycle??

Brittany • Pregnant with my Rainbow Baby🌈💜
I had a miscarriage March 30th. My HCG levels were back to 0 by the next week. My husband and I weren't TTC but we were preventing either. AF should have showed up last week but never did and I didn't think much of it bc I know it can take a little longer after a miscarriage. But today I took a hpt just for the hell of it and it was positive. It took me completely off guard. Does this happen often? I'm terrified to be excited but it's nearly impossible not to be. Anyone have any insight on this?