Returning to work / refusal of bottle

My LO (almost 3mo old) recently had a cold & the dr recommended allowing him to BF as often as he would to help keep hydrated and to get antibodies. I ran out of stored milk for bottles around that time. He would drink one 4oz bottle with rice at least once daily with no issues. He has GERD/acid reflux/colick. We are currently giving him Prevacid per his pediatrician. I was supposed to return to

Work today but couldn’t bc my LO will not take the bottle and I have no stored BM bc my LO has been nursing a little every hour! I’m exhausted and he refuses to try formula even if mixed with my milk. Any ideas or tips to help with this??