History:
Me: 26 years old, never been married, often in long term relationships
Him: 30 years old, been engaged once before, often in short relationships
Us: Together three and a half years, engaged over 1 and a half years; we have lived together for probably at least 2 years and we recently moved into a cute new house and he began talking about how he wants us to start a family and I was agreeable

Situation:
My fiance told me a little over a month ago (2 weeks after we moved - signing a years lease) that he has "feelings" for his coworker. It started out as "feelings" and is now described as a work crush. He told me this when he was drunk, I think because of an incriminating text message I saw him send her. "Let's disappear" was the exact text I saw (he had sent it while they were at a work outing) and I demanded an explanation. That is when I asked if he liked her, he said "I need to preface this with I've never cheated on you, but yes I have feelings for her." When he told me it was my automatic assumption that he was leaving me for her, I didn't stick around to find out more, in my mind it was over. I left that night in tears to stay at our friends place, I had thrown his phone in my purse. Later that night I decided to text her, "do you want to be with me?" I wrote. She text back, "Yes, but I want to do it the right way" as if 1) this was not the first time this had been discussed and 2) that she wanted him to break up with me (and her to break up with her bf). I know it wasn't right of me to text her, but I had hoped that if he cheated she would've indicated something like how they were already together.

When my fiance and I spoke a day or so later, he told me that he did not want to be with her. Even though he knew about her returning the feelings. I also asked why it had seemed like they had already talked about this, and he told me that once at work some guy was flirting with her and that he acted jealous and she asked him what was up and he told her that he had a crush on her. Also that she had asked him what the deal was with them, and that he had told her that he wanted to be with me.

Since that has happened a little over a month ago, we have been living together still. He tells me everyday that he loves me, tells me that I am the love of his life and how he wants us to grow old together. I don't feel like the love of his life; I won't pretend I am a saint, I have had work crushes in the past, I think it is apart of life, but I also NEVER pursue them, never tell them, never talk to them outside of work, I know that it is typically superficial feelings... I really don't know what to do. I do love him, but I don't know if I know how to get past this or if I should even try.