I still don't understand his crying :/

I read somewhere that you can understand every Babies cry by like 2 months.. my son is going to be three months soon and I still don't know what every cry means.. for example today he didn't eat for four hours and he started crying so I started to feed him and he spit up all his food while I was feeding him. (During the day I bottle feed him, and during the night I breastfeed him) he didn't seem all that interested in eating anymore after sitting up his food. I don't know what his cries mean and it's frustrating me :/