What do you think I should do?

my son will be 6 weeks old on thursday. I didnt feed him so i gave him Similac advance and he was on it until he was 4 weeks old, we took him to the dr. and he switched us to similac sensative because he was very fussy and gy. so know im using Similac sensative and ive been using it for a little over a week, but have noticed that he is still gy and fussy. Im using the playtex drop ins bottles,mylocon drops,little tummies gripe water(but i read that it has sodium bicarbonate and in the internet it says that its bad for babies and its not fda approved, so i really dont want to use this product anymore) and i also try burping him every ounce he eats, but with this formula he doesnt want to burp as much or its harder for him to burp. So I dont know what to do should i take him back to the dr. so he could switch his formula again or should i wait to see if he is still getting use to this formula? I really dont want to keep on switching formulas either because i read that it hurts their stomach. how long does it take for a different formula to take effect? and will his gas ever improve as he gets older? Sorry its so long but i have to do something my LO seems so miserable and he hardly smiles as much as he use to! Thanks