Why am I so bothered by this?

My fiance and I met about three months after he divorced his ex wife. Which he was very much in love with. Though I didn't know any of this until months later in our relationship. I may had been the rebound to be honest and had no idea. But whatever.... I am now his fiancé.

From the little bit that I know, they were together for 9 months according to him. And I just recently found out they married while they went on a trip to Vegas.

We went to Vegas about a month ago. And we argued almost our entire trip. He wasnt being the nicest person but we also had our good times. He said he hadn't been to vegas in about three years. Which adds up to when he was with his ex. Meaning that was the last time he went and the time he got married as well. And he hasn't been there ever since. I recently found this out. And Now I can't stop thinking about that trip we took to vegas ourselves. I feel like all he was thinking about was his Ex wife. I'm sure memories came up. And I can't who but feel mad about this. Now I can't stop thinking about how fast he married her but we've been together for two years and we're only engaged. And we argue. And we have a baby now. I know that he loves me but probably doenst love me as much as he loved her.

She used to tell him what to do. She was the leader in their relationship. If I was to do that, yes I admit he will let me sometimes but he's more dominant than me. I am more easy going and just go with what he says. Mainly because I am younger than him and feel I'm not very experience. She was rich, nice car and he never had to worry about supporting her. I am poor, I'm a stay at home mom and he's the sole provider who struggles with money and we're always stressing about our bills.

Before leaving to Vegas he joked about us getting married over there. And now knowing that's where he married his ex, makes me mad. Was he thinking about her the whole trip? Does he love me the same? Idk.