Breastfeeding Troubles

Lauren
Oh ladies. Breastfeeding is so much harder than I imagined it would be! My LO is one month old today and is EBF. I'm wondering if my supply is low. 
In the beginning my breasts were super heroes, making immense amounts of milk. He could nurse on just one side and be done for a few hours. Now we do both sides. 
I still have a super strong letdown and he spends the first 3-5 minutes literally chugging milk...huge gulps after every suck. But he is often done nursing before 15 minutes are up. Is this normal? I worry that I'm running out of milk before he gets his fill. 
Help would be greatly appreciated!