I'm not sure if this issue is now dead in the water, but, you have somehow gotten this man to finally have a relationship with his son. Why not leave it at that. Whatever begins to happen between you and the father may not be so good or end up so well and your son will be hurt and the man may not be so apt to continue to come around. Don't be selfish, let your son have him this time. There are very good or bad reasons why the two of you could and did not continue your relationship. Why have you been so isolated since your break up? Was it that bad? I would keep my dreams, thoughts and feelings to myself in this case, because this man has been 4 years without you, which proves that you have not been on his agenda, and much less, your son.
This may come across as mean, but to go for it makes you look desperate, and especially to him. It's been a long time, try something new. Don't be so willing to accept anything because you have allowed yourself to have nothing.
You may also be putting yourself in a position to be used,and get your feelings really hurt. Could the reason he has not come back around be because he knew that you would be bringing your heart back into the picture and he just wants to be free of you? Weigh everything before you do anything and move calculated and cautiously.
Don't louse up things for your son and his father because your flesh is weak. If this man has not come back into the picture telling you that he loves, wants and needs you and your son, then he may have someone and he is not interested. Four years without YOU should give you some hint.
Did you build your whole world around this man? So now you feel lonely and empty inside and it just doesn't seem right unless he is in this world or dreams? Come on, wake up, the man needs his son which does not necessarily means he needs you. Take all of the advice given and give it consideration, but look at it from this point of view also. Whatever you decide, pray and be real with yourself.
Nothing comes to sleepers but a dream.
Jen