The key word is boundries. Go take a hot bath, fix yourself some cocoa, crawl into bed with a pen and peice of paper. Then when you are all relaxed write down on the paper what it is that you want from a relationship. Once you have it out on paper in black and white you can start setting boundries that will help dictate just how you allow yourself to be treated. If you don't let him cross those boundries then he will not be able to screw you over again. The trick is to be firm and willing to say back off...or f*** off.
Take care,
Zen

PS sorry for the foul language but after a moment's hesitation I thought it was apropriate for the situation. Feel free to PM me and give me what for.

<font color=blue>"I am just so tired."
<font color=green>"You can say you're tired as much as you want but you still have to do something about it. Now can you think of any way to deal with this problem."
<font color=blue> "No"
<font color=green>"Then I don't know what I can do for you if you are not willing to try."--from Zen's therapy session