How can I change my name in college?

I've always hated my name: Megan. It's very popular, so I'm always turning around because someone was calling another Megan, and people always misspell it (Meghan, Meagan, etc). People also feel that they have license to call me "Meg," which I can't stand. I want to change to Gemma, with a hard G, which is an almost-anagram of my name, a little less common, and phonetic. Is this a good name, or am I going to end up regretting this as much as a tattoo?