My 13 month old has always had a milk protein allergy and has been on soy formula almost since…

My 13 month old has always had a milk protein allergy and has been on soy formula almost since birth. When she turned 1 year we moved her to emfamil toddler soy but she started spitting up and having constipation. Dr then put us on nutramigen toddler but it's just too expensive so we tried lactaid but she definitely couldn't tolerate it! We tried silk for almost a week and she kept it down but got a rash everywhere so we stopped. Does anyone have any suggestions. She's still on the nutramigen but at $28 for a 12oz can we have to try something else.