So there was no undue pressure -- just a decision by both of the other people in the car to implicate you. There was nothing that would have stopped you from saying, "It was not mine" or "They're lying". I'm not sure why you believed your friends would have abandoned you if you stood up for yourself, but if that's the sort of people you were hanging out with it's an object lesson in making better choices of friends and traveling companions.
"It really did belong to the driver" works better if the drugs aren't divided between a driver and a passenger.
You can tell your lawyer that the driver is now willing to say that he lied to implicate you, and your lawyer can see if the passenger is also going to say that he lied; your lawyer can advise you based on that, as to your best options going forward.

