2 month old baby boy is constipated?

i have a two month old son who seems to have trouble using the bathroom he will strain for a long time and than start to cry and its so hard to calm him down, ive tried water and that really hasnt helped then i switched to prune juice and also tried alittle apple juice not much though and it still hasnt seemed to help im alittle hesitant to try the karo syrup because of the infant botulism but i dont know what to do i hate to see him cry, is there anything i can give him? would soy formula help or is there a better kind of formula i use gerber good start? any help would be so much appreciated.