Can't sign into Minecraft, forgot all my details?

A long time ago, an ex made me a Minecraft account for me. After a restore of my computer, I re-installed Minecraft. Now the main problem is, I have no idea what my account information is. I remember my log in name but my password I have not. I got an email sent to somewhere to re-set my password but I have a funny feeling it goes to his email address. What can I do about this. I really don't want to have to re-pay for Minecraft or loose my saved worlds…

I've been through the same thing and it is extremely complicated. Look for help on the Mojang site if your account is migrated to your Mojang account. But in the worst case, it's only 19.95 EUR for a new one.