Yes, you can call/email to ask if you truely love the new job.
However, since you do not have the card in your hand to play with, you do not need say you have offer in hand.
You may say: I got many phone calls and went very good interviews, however, I still prefer get offer from you. Where are we right now?
We had discuss about this topic in our previous Tuesday night's tele-conference, you can list it by lick [博客] on top of this page and find recorded tele-conference.
Thanks!