2 month old not eating properly

So we are in the transition from breastfeed to bottlefeed w/ breast milk . Intitally mt baby did not take any bottte. The only bottle he had some success was dr brown wide mouth . He would take abt 1.5 oz from bottle per feeding. I would feed him 3 times a day with bottle and the rest with breast . Today I had to go get some test done so my husband help me feed my baby. Throughout the day he kept sleeping and did not take bottle just an ounce from bottle . But he did not eat much from breast and kept falling asleep while breast feeding also . I am so worried. Just anyone had something like this experience. Pls help