3 month baby sleep and gas problem.

My 3 month baby falls asleep but not stays asleep for more than 15-30 min in daytime. He takes 8-9 hours of sleep at night(with feeding breaks). He has gained weight and wetting more than 8 diapers daily. But he wants to take feeding at almost every hour. I'm mostly breastfeeding him, twice or thrice a week I need to give him formula bottle if he seems very hungry. My breastmilk comes for 10-15 mins in one time, after that if i press and check, there is no milk coming so if he is awake, I change the side. He is also passing gas (farting and crying at the same time) very much, mostly more than 15-20 times a day(every time we take him on our shoulder for burping or put him down on bed ). I'm confused about what I'm doing wrong here.