It's easy for us to give you advice, but a lot harder to give you good advice because we're not living the details.
I will say this though. I was once in a similar situation (not with the lying) where I was with someone I cared about but just didn't feel the same connection anymore and wasn't happy. She felt the same way.
We dated for a little over 3 years and are still friends but I really wish I could have that time back. The problem, as I see it, in these situations is that if it doesn't work out you end up dwelling on what could have been.