Sudden behaviour changes don't bode well. You know this or you wouldn't be posting here. Try to find out the scoop, if you can. But be prepared for what WarriorMaiden said. A 5 year LDR with yet another 2 years to go isn't something most people would be satisfied with. Not sure if you are aware, but a lot of men use these types of relationships to 'feel' like they are in a relationship while living a single lifestyle. Even if you stick it out, I predict a breakup just as you are planning to move together. Sorry, but that's how it works.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh