help- too much spit up?

Erin
My baby will be 5 months next week. She has been drinking 6oz bottles every 2.5 to 3hrs for a while now. She sleeps 12hrs overnight without waking up to eat so she gets 5 bottles in a day (30oz). Her dr was fine with this at her 4 month appointment and is aware that she has always spit up a lot, so it's not something new. She's never upset when she spits up. In fact, she usually smiles about it. It's not always immediately after a bottle, it can be hours lately, and it's not always after every bottle. She's usually pretty good with burping during bottles. Sometimes she spits up so much though that I feel like half the bottle is gone! Isn't that a sign of her belly being too full? I don't wanna bring her oz down because she's a great sleeper so she's still only going to get 5 bottles in a day between all her naps and I don't want to cut her daily amount. Any suggestions? The doctor always says the spit up is normal, I just worry I'm filling her belly too much. First time mom here!