Ok i have a question i love it when my bf sucks on my boobs but i dont kno what i should be doing when he is doing it. i dont wanna just lay there what can i do to turn him on while doing it?? and how can i get him to do it harder with out tellling him?

Just imagine you getting a body massage. Don't you ooh! and aah! when the masseur(se) hits the right spot? It is not intentional nor do you have to think of how to react, do you? Same applies; if it really feels good then I am sure you would react to it naturally, your way.

There are many things I do, whilst.

Run my fingers through his hair, softly or otherwise.
Press his head closer as he increases the intensity.
Rub my body against his.
Hold area between his neck and jaws and pull him a little harder towards me.
If he has his hands elsewhere then I would get hold of them and make him play with them during.
If his hands are already doing so then I would place my hand over his and make him press them harder or roll them or knead them, as I feel like.
Pull his face up to me and kiss him in between.
Join him in the act of licking and sucking mine.
Run my toes up and down his legs and buttocks.
Kiss and lick and bite his nipples as and when.
Bite him on his shoulders or dig my nails deep in his flesh.
Hold his in my hand(s) and rub it and massage it.
Make him realise how wet he has made me, in different ways.
Combination and a mix and match of all the above and million other things, as and how I feel like.

These are the things I do or feel like, need not be the things you would want to. Just a single advice which might help you, if you feel a little conscious of “What should I do?”, the best way is to let go. *wishes luck*

you really don't need to put on a show. Don't be fake. Just do what you normally do. If you just lay there, then just lay there.
You can always touch him in someway

Communication is the key to great sex...why not just tell him what you want/like? Sometimes us guys need a little prodding in the right direction to behave as you want.