How do you get rid of him?
Keep a mental note of where all his crap is. Maybe gather it together on the pretext of tidying.
When he leaves the house, put it all in binbags, tie them tight, put them outside.
Send him a text saying, 'I can't live with you anymore. Collect your stuff, and take it to your Mums.'
*If he has a key, go to a DIY store and buy some new ones, if they are the cylinder type that slide in and out from the side of the door (check - you can tell easily, is there a screw holding the lock in when you look at the edge of the door? All you have to do is take it out, measure it - some barrels are 50mm each side, some are 60/40 and you need to buy a replacement that's the same. Just turn the new key in the new lock until the barrel lines up, put in the door, and screw it in. It's much simpler than I'm making it sound, look at a YouTube video!) Keep the new keys hidden away, and change them as soon as you put his stuff out.
If he causes any trouble, report him to the police. And of course we'll offer moral support (but NOT on the AIBU board, start a thread in Relationships!)