I've realised that a lot of the perks ive chosen i no longer need and was wondering if there is any way to undo my perks and pick new ones? i don't want to hav to start again because ive put a lot of time into my character. If anyone knows if its possible please let me know?

nop

No, and i'm glad. It's one of the redeemable things about an otherwise poor levelling system.

If you're on the PC, there probably will be a mod.