My (F23) relationship with my bf (M24) does he want to be with me?

Hi everyone, throwaway account obvz. Me and my bf have have been together for almost 2 years and living together for most of that. We've been going through some things lately and I've found a few things out that have just made me a little uneasy I guess.

My boyfriend has told me since day 1 I'm his soulmate, he never wants to be with anyone else, he's going to marry me, etc. I feel the exact same way about him. But we've hit a few rough patches and I understand relationships go through that; but even during the roughest times I know that I want to spend my life with him. Well last night we got into a pretty bad fight. He told me that he was doubting whether or not he wanted to be with other people and sometimes he wondered if he could get someone hotter. But he didn't say these things to be hurtful. This was after our fight. We were having a heart to heart and he told me they were some thoughts he had been having.

There's also a girl we work with and he said he may have a had a crush on her a few months ago and that he might have thought about wanting to be with her instead. I know I have some insecurities to work through and I'm sure that's why all of this has hurt me so badly. But at the same time, I've never questioned how I feel about him or wondered if I could do better. I'm just not really sure what to feel right now. I'm feeling sad, hurt, lost, and confused.

Today has been better. He told me that he knows he wants to be with me for the rest of his life and that it's normal to question things from time to time and that it's just human nature. He also said he didn't want to be with anyone hotter, it's just something he wondered (idk why he even told me that bc now it's stuck in my brain).

Idk guys. Like I said I have some insecurities I know that. But how do I move on and not dwell on the things he said to me? I want to be happy again and make him happy again but it's so hard to act happy when I feel so blue.

TL;DR boyfriend of 2 years said he doubts us from time to time and sometimes wonders if he could get someone hotter during a heart to heart. How do I not dwell on those things and be happy with him again?