Is my relationship over?

Okay so I have been with my fiancé for over 5 years. We have had a lot of ups and downs but have managed to stay together. Two weeks ago we got in an argument and he threw his iPad across the room breaking it. We ended up breaking up. Well, I felt pretty lousy about breaking up with him and to my surprise he texted me two days later asking me to come over telling me how much he loved me and how miserable he was without me. He even said he broke down at work. He was so nice that night pouring his heart out. We made back up and he read me a sweet love letter he'd written to me. The following weekend was also wonderful. I felt we had really brought the spark back and thought we would find a way to work things out. Well yesterday stuff hit the fan. We had an awesome day together and he got a little drunk. I started talking about our relationship. I told him I loved him and still wanted to marry him. He responded sarcastically as if he didn't believe me. When I said I loved him he didn't say it back, choosing instead to say "thank ya." He pretty much disregarded my feelings completely and it was devastating. I cried myself to sleep last night. How could he change so much in such a short period of time? It was almost as if he regretted apologizing to me two weeks ago and admitting that he had cried. It was like he was suddenly full of pride and detached from the relationship. He just didn't care! What should I do?

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