Baby Seem Constipated?

Hi mummies, my little one is 1 month old. Mix feed (BM n Fm). Currently on similac total comfort..she seem to have alot of air n cry /use force to let out air. And for poo she seem to be in pain trying to poo out but eventually did and she is happy again. Would you know if this is due to: 1) mix feed 2) Fm problem so need to change? 3)bm problem Coz I'm drink too much red date tea? 4)colic?