My computer just got formatted, and so did my wallet. I had imported the private keys from my wallet a week back. Can I just load that again into multibit, and get my bitcoins back?
I have also had several transactions after I imported it
Yes, you can. The private keys unlock your wallet, which will be synchronised to the network. You then have access to the wallet, with the bitcoins before and after the back-up of the private keys, just the balance blockchain.info says you have. So no need to have an recent back-up of those keys.