Something odd happened to my account - I think it has something to do with the merge I tried to do a while back. I have another account on the RPG stack exchange, and I attempted to merge that account with MSE, because privileges and whatnot. Instead, it seems I've lost the reputation I had on MSE, but kept in on the mathematics meta? I don't quite understand. It's not like it's super important - it's just a few hundred points, and I'm definitely not as qualified as most of the other mathematicians on this site. I just want to know what exactly happened so that I can avoid it in the future.
A likely cause: you used different OpenId providers (e.g., Google and Facebook) for the two sites. In this case you may be able to fix the problem yourself. Click "my logins" in the user profile, select "add more logins" and add the OpenId you used for the other Math.SE account. When the system detects two accounts with the same credentials, it should automatically merge them.