Do you tell your guy if you don't get want you want then your gone? Do you say it angrily? If you think this is going to work, you are greatly mistaken! Nothing drives a man further away from you than giving him an ultimatum, this makes him cringe.
If you have been dating for years, it's understandable that you want things to move to the next level, you want a man that is serious about you and only you and wants to commit, propose and marry you.
Forcing a guy to commit to you who's heart isn't really into it could cause greater heartache in the long run. Divorce is one of them, this is emotionally painful and can also be so financially..Check out this article of how divorce is very common in the United States http://www.cnn.com/2013/12/09/opinion/schwartz-baby-boomer-divorce/. You don't want to become just another statistic by forcing your man to commit to you and eventually marry you.