
Sister, having a relationship before marriage is forbidden. The correct way to get married is for a man to approach your wali for permission to marry you. Then you can meet in the presence of your wali and see whether you are compatible. You should not seek to be alone with a guy without the presence of your wali. Unfortunately, by not following these rules, situations like yours develop.
However, what's done is done. Move on, repent and when you get any more proposals in future, adopt the method specified above inshaAllah.
In the case of this particular guy, you have two options.
1. You refuse him outright cos of his past behaviour. Frankly, I think this would be the best option.
2. You tell him to approach your wali if you are willing to give him a second chance. Don't let him come up with excuses as to why he cannot. If it is serious, get family involved else if he hesitates on this even one bit, move on without giving him a second thought.
Don't forget Istikarah salah.