Help please I dont know what to do?

I have a special needs son who is almost 2 and a 4 yr old. My sons first dr. would never see my son it was like her istant and she always gave the most horrible advice my son is small for his age he looks like a baby he wears 6 and 9 month (16 lbs 27 in) clothes and she would tell me he is too small feed him more and all that did was make him have projectile vomiting and become very fat! So i stopped taking him and the doctor had the nerve to call me and say i don't care about my son and that if I don't take him to see her she is calling CPS! Needless to say I got a new doctor for my sons and I asked this dr. questions and he never answered any of them or referred me to any other doctor that may have answers! I still don't even know what to feed my son he only takes formula because he cant eat not even with baby food in a bottle! I am starting to go a little crazy having no answers and not knowing what to do! I went to WIC to get help with formula since he is over 1 they said Id have to have a doctors prescription and the doctor hasn't given the prescription to me because he doesn't know what my son should be eating! The people at WIC also said my sons Iron was low thats all they checked so who knows he could be not getting enough of any of the vitamins and stuff he needs! I am getting stressed he still sees his specialist doctors but they are just specialist not for general stuff! Should I take him to the ER? Is there actually a doctor out there who cares??? BTW I live in Oak Cliff so hopefully a doc nearby?