OH WOW I NEED HELP WITH MY SCREENPLAY.?

I'm going a little nutzo over here. I've been in the rewite process for nearly a year and I told myself that I wouldn't move on to my next idea (which I'm dying to get into) until I finish my current project. Basically, my problem is that I have everything outlined, everything mapped out, everything fits into the guidelines and plot points of where things should be, and it's still too long. I'm aiming for 120 pages (as every screenwriter does) and I always get somewhere around 140-150, and that's even after shaving off scenes, cutting out long descriptions, conversations, and phantom lines, and all that stuff. I don't know what else to do, becuase if I cut any more out, the story loses its cohesive quality. Anybody ever dealt with this? How on earth did you solve it?