Advice needed - baby refusing milk

Hi, my son is currently 10 weeks old and currently bottle fed expressed breast milk. Recently he takes more than an hour, sometimes 1.5 hours to finish his milk. He is very gassy and squirms alot during the feed so we need to burp him a couple times between feeds. Sometimes, he even falls asleep from feeding 🤦🏻‍♂️ He usually goes 3 hours between feeds (sometimes 4 hours depends on his cue) PS: I start counting from the time we start the bottle feed. He is currently on 3m teat and taking ridwind drops for his grassiness. Does anyone have any advice on how to help this frustrated mom? Thanks very much in advance! 🙏🏻😫#pleasehelp