I'm worried my period is actually an early miscarriage. are there any sure signs that would help me tell one way or the other?

Beta hcg test: If your period is at the right time, why are you worried that you were pregnant/miscarrying? There typically isn't any "sign" you could look for to know if you were pregnant since it would have been so early on. A beta hcg test from your blood can show if you were pregnant if you get it done quickly before it goes back to normal within a week or so of a miscarriage. See your doctor to discuss.