just explain that having had several years devoted to a serious relationship you need time to re figure out your needs as an individual person before going to couple status again...

if he can't understand that, than i'd suggest you give him the "let's just be friends" line, until you have yourself ironed out in your new status as single, how would you be able to iron out the going feelings of one man, the incoming requirements of another man and your own feelings as an individual who's just had a major shift in their life?

divide and conquer, establishing your own kingdom, then you can enjoy the spoils of war in unity with another.