katie,
There are many, many wise voices here and I want to echo Pelican as well. When I had the last counseling session with my exA I made the decision to fill my car with the things she had stored in my attic and give them to her after the "break up counseling session". You can read my posts on that, it was not an easy decision. But now, 4 months later, I can see that it was one of the best decisions for me that I could have made! I needed her to be out of my life so I could heal. I needed to make myself the priority. She was very upset but I was taking care of myself. Her reaction was a good clue as to how much she really respected ME--not much. It was always about her.
If your situation is anything like mine your exbf will be upset no matter what you do--it's a double-bind, you can't win, you can't make the "right" choice so that he'll be happy.
I had a friend who, after repeated asking her exbf to pick up his stuff and he didn't, rented a storage facility for 1 month. She put her bf's things in it and mailed him the keys to the lock. She told him that after a month the facility would be able to sell everything if he didn't either pick the stuff up or pay the rent. Either way, she was out of the middle. I'll bet he wasn't happy, but SHE was, and it was no longer her problem.
Oh, and she changed the locks, too...after he waltzed into the place while she was at work and stole some of her stuff. Of course, he said he DIDN'T take the items. But after the locks changed there was never a problem again.
Big hugs,
posie