Why does my boyfriend want a break after 3 years off and on? how do i give him the space he needs?or should i?

My boyfriend and i have been together 3 years off and on, (more on than off). When we were together just a few months he wanted a break, i gave it to him and nothing really changed we talked and hung out just the same. Then we ended up breaking up. So this time he is saying suddenly out of the blue that he wants a break. I dont know where this came from and so it is difficult for me to give him the space he needs since i dont think i did anything wrong? what should i do, to give him the space he needs. I really dont want to break up. we basically live together and we have a puppy together. he told me i am smothering him and his friends have told him that he is whipped so that probably has a lot to do with it. His family also told him it is time to think about marriage (which i am not ready for) and now he seems to think that the only next step is marriage. Can this be the only reason for the freak out and the sudden need for a break? basically i just want to know what i need to do to give him space enough to make things get back to normal...