Tips for helping baby gain more weight

My baby is 10 weeks and has been slow to gain weight since birth. Overall he has averaged about .7 ounces of weight gain a day instead of the 1 oz/day recommendation.

He is ebf, my supply is fine, and multiple weighted feeds have shown that he transfers milk well and takes in a normal amount. He spits up quite a lot so we have started him on a reflux med and still waiting for it to work.

Any tips on helping him gain weight faster? I don’t want to do formula because it is expensive and my supply is fine. I also am concerned that if he starts taking more bottles (currently gets 1 bottle of breast milk at night) that he’ll prefer that over nursing and I then have to pump more which I don’t really like.

Also any encouragement from moms who have dealt with a similar experience would be appreciated!