|I don't think anybody here can help you on this.|
If your ex knew your original password then he/she could have gone and changed all your settings so that he/she appears to be the owner of the account and not you.
Your only hope is to contact hotmail and try to explain your situation to them. I don't know how easy that is going to be for you.
This just illustrates how important it is that you do not share your passwords, PIN numbers, etc with even your nearest and dearest.
Have a look at the following two links and see if it helps:
The second link is probably the one that may be of use to you.
☺ When everything else fails, read the instructions.