My current boyfriend (22M) had a girlfriend when him and I (22F) started talking. What now?

I recently found out that my current boyfriend had a girlfriend while we were talking. He consistently told me he loved me and when I asked he said he was single. All the while he had a girlfriend. I started to think when I was in bed about how he told me I could always call him and before we were together I took him up on that offer and he was furious when I called and I didn't understand why. Not until now at least. I asked about it and turns out he was in fact with his girlfriend. My blood is still boiling and I don't know how to feel. He had made so many promises to me and assured me he was quote"waiting for the right person". I hate the idea of being the other woman and having our relationship flourish with lies. He told me that he chose me over everything. Does this mean I should be grateful? What happens now?