First sign of miscarriage?

What is typically the first sign? I’ve had a feeling like my period is coming off and on for a week. Yesterday, I didn’t feel it at all, but today, it’s the strongest it’s been with moderate-severe cramping. I haven’t seen a drop of blood. Is this typical? I know they say mild cramping is typical in pregnancy, but I would no longer call this mild. I’m just wondering when to expect bleeding. Thanks for the insight.