Newborn has diarrhea using gentlease from enfamil?

im so confused my 2 1/2 month old newborn son was very gy and fussy, he wouldnt sleep well- would wake up after 20 or 30 min of nap so i switched him from enfamil premium to a gentle formula from sams club and it was fine . anyways because of my finance situation i am on wic and switched him to gentlease from enfamil becasue that of course i cant use sams club brand, and now ever since he has diarrhea, since saturday 2/20 my doc advice to put him on pedialyte for 1 day to cleanse out then back to the gentelease so i did still the same and now its very slimy and mucousy looking yellowish brownish .this was on wednesday 2/24. sometimes he seem to rub the side of his face by his temples so i ws afraid he might hav a ear /infection so i call his doc today sunday and he says well lets try to swtch him to a soy formula and see or just go back to sams club .. he doesnt thnk he has an ear infection bcz no runny nose or cough..and no fever so now am so confused on what to do if i go back to sams club i cant afford if i try a soy ? what if i irrate his systen even more.. what if it is more than just the milk that causing diarrhea for abt 10 days now..