Good evening girls. My son is 3 months old, he's been sucking for abou…

Good evening girls. My son is 3 months old, he's been sucking for about 3 weeks and he usually takes 5-7 minutes at a time and cries hysterically. He doesn't take anything after that. Almost every feeding. Before that, he could suck for 10-15 minutes. I'm sure there's enough milk, it just flows out. I hear him swallow, and it comes out of his mouth. Only if you hold him upright does he calm down. It doesn't always come up with burping. What could this be related to? The child is second, he had no problems with the first one.