Take a week off don't speak don't write don't call.  If in that week you felt so heartbroken as if your world was crashing around you..and they felt the same way ...Then you need to stop and think of the future when your 80 sitting on your front porch can you picture that person sitting next to you..now can you picture them not...If you cannot picture them there no matter what condition they are in and you still want them then it is meant to be and you should get married have kids a be faithful to one another.  WARNING BOTH PARTNERS HAVE TO AGREE TO THE SAME FEELINGS..otherwise prepare for a divorce now.
how do you know if you really love someone and want to spend the rest of your life with them how do you know?