1 month old. Formula & spit up

My one month old baby has so much spit up almost after every feeding. He drinks 3 ounces every 3 hours. He spits up so much and it's really hard to burp him. I told the doctor about it but he insists that it's normal. What's the normal amount of spit up a baby should have? He won't change his formula and I don't know what to do. He had spit up in his sleep three times tonight and I haven't slept cause I'm watching over him. It was really hard to burp him and he's had gas all night too. Also, twice tonight he only drank an ounce and a half. Is this normal? He had a hard time falling asleep, so maybe that's why he didn't really want to eat much, but it could also be the gas that has his tummy feeling full. Is there anything I can do about any of this to help him?