It sounds like you are mourning the fact that you two didn't get along and are hoping for a do-over. You can't get back the same relationship you had before, and really and truly, you don't want that old relationship back. Instead, you want to forge a new relationship, one that is between an older adult and a young adult. Instead of wanting him to stick around and help him out and "be there" for him, try to look at it like allowing him to spread his wings and learn how to be independent. Boys need to learn to be men. Instead of "fixing" his problems, ask him what he plans to do when he has a problem or issue. Give advice, but don't push. Don't offer to fix something for him. Give him the tools to fix things himself. Truly, if he isn't expected to fix his own mistakes or handle problems, how will he ever learn?
I do think that perhaps you have peri-menopause or menopause going on, and you should go have your hormones checked. If they are low, consider HRT at least for a while, to help you through this.
At graduation, take your camera and take 500 pictures. It will give you something to "do" and hopefully help you keep from weeping. Believe me, you want to act happy for your son instead of making him uncomfortable and embarrassed because you can't hold it together.
It is supposed to be a happy time for him. Please let him have a happy graduation by not crying through it. If you feel that you can't do this, ask the doctor for some help once you have had your hormones checked.
Hugs, Mom!
Dawn