Need help and advice please

Need some advice please

Af ended a week ago today , but I’m cramping and bad back pain exactly like how I feel on on day one an day two of AF for the sake of it , I took a HPT and a OPK and both are big negatives like the opk doesn’t have any second line , any any idea what this could be I’m a little worried I’m two months over a miscarriage and I’m stressing