Could ask him if he's willing to do jealousy work
or not. If not?
Call it you are basically not compatible -- stay broken up. Because you cannot force him to do jealousy work if he's just not willing to do it. You have already been here a few times with this problem -- if you are willing to try and he is not willing? It's still NOT BOTH WILLING. Not compatible.
Do the work of the stages of grief
for the loss of relationship.
At 20? You have just begun having your adult experiences. Life is long, and don't have to have them all up at the front end of your adult life. Learn to be ok with the good, fun to feel experiences and the ugh, not fun to feel experiences. That the business of the 20's -- gathering experience yardsticks to help you navigate other decades.
You will be ok, honest.
Hang in there and process what you have to process.