Periods on birthcontrol!

Okay I just need advice. I started the pill Birthcontrol method back in like April, obviously my periods changed. Use to they were HEAVY and lasted 4-5 days. Now they’ve gotten to the point where my period is maybe 3 days, only one of which is moderately heavy. The other light days I usually don’t even need a tampon. Is this normal? Every month I panick into the AM I PREGNANT mode and freak myself out. However my periods are consistent, and I haven’t had any unprotected sex on birth control. What’s normal for periods on the pill method?