Why won't my ex give me my stuff back?

Anonymous
My ex broke up with me after a 2 years of breaking up/back together a week later on a monthly basis. He tends to just ignore me, delete me from everything, block me on FB, etc and tells me to never contact him. Then he comes to his senses, gets back together and loves me the next week. (Perhaps a little bipolar?) Anyways, this last one was the big breakup. He hasn't talked to me in 2 weeks (longer than he has ever done), did his normal routine, etc. I have messaged him repetitively to get him back, or get my stuff, or to get over being angry with me since this is what he wanted. He has some things of personal value as well as the key to my apartment yet he has yet to give them back, or even contact me back about when I can get my stuff. Normally he puts on a show and rubs it in by asking when he could get HIS stuff back so he would have the upper hand, but he said nothing! 3 weeks ago we had a fight, made up, he bought me expensive roses (which he never does), then a week later breaks up with me again because he claims he lost feelings for me. (even though he loves me a week later then doesn't love me the next)

My questions:

Why is he doing this?

Why so eager to give my stuff to me on previous breakups, and now he won't?

Why ignore someone and convince yourself you don't love her?

Whats with the flip-flop back and forth loving me then not?
Why won't my ex give me my stuff back?
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