I'm concerned about my identity security

I registered with Credit Karma last week and when I couldn't log in, customer support told me that someone using my name already registered over a year ago with a Hotmail address I don't recognize. Well Credit Karma wasn't a great deal of help, so they can't confirm if this was just some bug w/their portal or if someone has been trying to steal my identity by looking up my credit history. So I put a fraud alert on my credit account w/TransUnion and Equifax and I'm thinking of a credit freeze. Then I made a report w/the federal government's fraud reporting web site. I'm not sure what to expect now. I only discovered this a year after the fact, and I haven't noticed any unauthorized use of my credit, so just how useful was my credit data?
The only reason I found out about this is I'm looking at getting a government loan and they say you should look at your credit rating when doing this sort of thing. But it seems you should be doing it every so often even if you aren't looking at getting a loan any time soon!