He gave it up for the wrong reason if the only reason he quit was because you didn't like it.
As Julie said, get yourself to al-anon or some similar group for support, and to an attorney. By the sound of your post you're not only thinking of divorce but contemplating an affair because you're "lonely." Get over it, and get yourself straight before you start complicating your situation further. You've been married 2 1/2 years, divorce will likely be (relatively) simple if you don't have children together. If you decide to stay in the marriage, you need to do it knowing you'll be faithful.
Good luck, keep us posted.
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