Baby very fussy for milk. Bottlefeed.

My 4 month old baby is mostly bottlefed..sometimes expressed breastmilk but mostly formula..becos i have low milk supply breastfeeding is not done much..of late she has become too fussy..like pushing away feeding bottle, crying, moving head sideways and spittin out milk etc.. If i try to breastfeed maximum she wil suck for few mins and cry.. Spoon feed or palada feed also she doesnt take and hates palada.. Bottlefeed she takes only occasionaly when hungry that too little bit only...she usually takes less than 700 ml per day...her milk intake does not cross 800 ml per day... Im very worried and upset...today i tried giving breastfeed and she started crying hence i had to give bottlefeed...that also she drank only after much effort on my part. If i try on demand feed sometimes she does not get hungry for many hours at a stretch...and then gas forms.. Pls advice waht to do.