Someone used my apple ID to access my emails, imessages and facetime.

Set up 2 factor authentication. Now.

Frequently asked questions about two-step verification for Apple ID - Apple Support

MMHRN wrote:

Can anyone shed light on how this happened? Why?

Not really. I mean, we can definitely say that someone hacked into your Apple ID/iCloud account. Who did it, why and how it was done is not something we can answer. It could be someone you know who managed to guess your password, based on personal knowledge about you, in an attempt to mess with you or harass you. It could be a total stranger who hacked your account through brute force, aided by a weak password on the account, in order to use the account for purchases. It could be someone who has hacked one of your other accounts that had the same password as your Apple ID.

Dwelling too much on the who, why and how isn't productive. You'll probably never know. Just focus on securing the account now. Make sure you go back on March 1 and finish the two-factor verification process. When you do, make sure you store the recovery key somewhere secure, because if you lose that and forget your password, you'll never be able to use your Apple ID again. In the meantime, make sure you have set a strong password on the account... longer is better, but it doesn't have to be complex. A password that is long but simple, like "I like apples and bananas!", is better than something short but complex, like "kn352!fn". Provided, of course, that your long-but-simple password isn't easily guessable based on knowledge of you, or because it's a common phrase (such as "The quick brown fox jumped over the lazy dogs").

To add to the advice from thomas_r. (which I agree with completely), if you are in the habit of using the same password for multiple accounts change every one of them that is the same as your Apple ID password. And make them all different from each other. One way to do that is to create a good, long, password, then add something from the site that you use it with to the password. An example might be the first and last letter of the site name. for example, if you had an account with Capital One, and your base password was "mydoghasfleas" (not a good choice, BTW) then the Capital One password would be "cmydoghasflease"

Lawrence Finch wrote:

if you are in the habit of using the same password for multiple accounts change every one of them that is the same as your Apple ID password. And make them all different from each other.

Excellent point. A password manager like 1Password, or even iCloud Keychain, can help with that.