Im not one for playing a game more than once no matter how great it is, so wanted to do everything i could in 1 playthrough. Is it possible to do all faction questlines or eventually do you have to side with 1, thus locking out the others?

You have at one point side with a faction and make two others hostile.

There are post conclusion quests, so you can not do them all in one play through. For most of us, Bethesda games are a way of life, so it is hard to imagine only one play through.