Really unsettled baby

My 3 month old has been pretty unsettled the last few days and has been drinking less and less each day and crying during feeds which is concerning as the last time this happened she ended up in hospital where she was diagnosed with a Cows Milk protein allergy, a soy protein allergy and I was told that she can't have goats milk either. She is constantly sucking on her hands but doesn't seem to be hungry. She has been spitting up more than usual but doesn't have a temperature. Usually she will take her dummy but she constantly spits it out now. She is also constantly licking my hand or trying to bite when I try to burp her. She also coarsely suffers from constipation and trapped wind but will settle and sleep if I'm holding her which I'm hoping to avoid doing again as she's only recently started sleeping in her bassinet without a problem again. Can anyone give me any advice on what could be wrong and how to deal with this sudden change in her please