I think not
If you haven't already, absolutely not! The amount of time they've been going out is really none of your business. They could fall in love within a month and decide that they want to be together. You really have no right to meddle. He obviously doesn't love you because he's about to marry someone else.
Do you really beleive that he would break her heart for you? If that were the case, he would be engaged to marry you, not her. Furthermore, what you should be asking is what sight they met on so you can find your own.