My boyfriend is depressed,im feeling worthless what to do?advice plz?

So i have this boyfriend and hes been going thru alot lately,he has been actin weird the last couple days,i asked him if there was something wrong he sed he was sad but he sed he didnt want to talk about it.everytime i text him or something he just replies.with yup,o ye ,mm,or with a dot (.) i dont know what to do,i been with him for almost 8 months,i feel helpless i dont kno what to say when he says fml or :( ,im not good at this things.i dont see him that much btu i do talk to him everyday,he makes me feel sad too and i do not want to break up with him...life is so ughh! hes ex lady is prego and idk what to think because he was w her wen she got prego and it can prolly be hiz? i dont kno what to think or do anymore,i love him , any advice on what to do? or how to make him happy and let him know im here for him? N0 DIRTY STUFF PLZ!! but ye :/