I don’t know what to do..

I’ve been with my husband since 2017. I was 19 when I met him, and he was my first real boyfriend, so I’ve never really experienced another serious relationship.
Before me, he cheated on his high school girlfriend, who he was with for four years, and he also cheated on his college girlfriend, who he was with for three years. About four months into our relationship, he asked me if I would have a threesome. I said no, and then he suggested I sleep with another guy so I could experience being with someone else. I told him no to that too. The threesome thing also wasn’t just a one-time conversation. He has continued bringing it up throughout our relationship, including after my brain surgery and while I was going through chemo and radiation, even though I’ve always told him I’m not interested.
Not long after we started dating, I went to his apartment one day and noticed hair on the shower wall and toilet lid that wasn’t mine. I didn’t really confront him about it at the time. There were also multiple occasions where we went through each other’s phones, and our relationship became very toxic in that way. A few times when he went on guys’ trips or bachelor parties, I found emails showing that he had been on Tinder and Bumble.
I got pregnant with our first child in 2019. We got married in 2021, and I became pregnant with our second child shortly after. In February 2022, while I was pregnant, I found out I had a brain tumor after having symptoms on and off since 2015. After having our second baby, I had brain surgery in November 2022 and found out it was brain cancer. I then went through proton radiation and chemotherapy.
I know everything I went through was hard on both of us. Our kids sleep with me, so my husband sleeps in the guest bedroom. That’s the reason we normally don’t sleep in the same bed, but overall our marriage still feels more like we’re roommates. We occasionally go on date nights and take trips alone together, and we do still hook up, but there isn’t much closeness or connection in our everyday life.
There have also been multiple times when he has come home from work with a strong unfamiliar odor on him or I’ve noticed things physically that have made me suspicious. He is extremely good with words and has a very charming, likable personality with other people. He can talk to pretty much anyone and comes across very well, which makes things harder for me because I also know how convincing he can be when he wants to be.
Because of everything that has happened throughout our relationship, I don’t know when I’m picking up on something real versus when years of distrust are making me question everything.
I love him, and I really don’t want to leave. My cancer has been stable, but going through something like that completely changed the way I look at time. I don’t want to lose time with my kids or break up our family based only on suspicions. At the same time, I don’t want to spend my life in a marriage where I’m constantly wondering if I’m being cheated on.
I feel like we’re basically roommates who occasionally hook up, and I don’t know what to do anymore. I feel like I need concrete proof before I could ever make the decision to leave, but I also know our relationship has been toxic for a long time.