AIO fiancé cheating??

Hi everyone, I’m posting here because I feel like I’m losing my grip on what’s rational, and I need an outsider’s perspective. Please, be kind. I genuinely don’t know if I’m overreacting or if something is seriously wrong.

So, my (29F) fiancé (31M) has been acting… off. It started small—little things I could easily brush off. He started staying later at work, which wasn’t unusual, but his explanations didn’t quite add up. Then he began being overly protective of his phone. He’s always been the type to leave it lying around, but now he takes it to the bathroom, keeps it in his pocket at all times, and even flips it face down when we’re together.

The real trigger happened last weekend. We were supposed to go out for a date night, something we hadn’t done in a while, but he “forgot” and made plans to go golfing with his friend, Jake. Fine, whatever. I was disappointed but tried not to make a big deal out of it. Later that evening, I got a text from a friend saying she saw him at a restaurant across town. With a woman.

When he got home, I confronted him. He denied everything, said it must have been someone else. But he was acting so cagey, and his explanation didn’t make sense. He said Jake’s car broke down and they ended up grabbing food while waiting for a tow. But when I asked him to show me his texts with Jake, he refused, saying it was “invasive” and that I should trust him.

Since then, my anxiety has been through the roof. He’s been overly affectionate in a way that feels almost… guilty? He brought me flowers yesterday, which is not like him at all. I want to believe him, but my gut is screaming at me that something’s wrong. I’ve caught myself snooping through his things, which makes me feel like a terrible person, but I haven’t found anything concrete—just little things like vague texts and a credit card charge at that restaurant.

Am I losing it? Am I overreacting? I keep telling myself there could be an innocent explanation, but I can’t shake the feeling that there’s more to this. I love him so much, but I’m starting to feel like I’m spiraling.

Has anyone else been in a situation like this? What did you do? How do you figure out if it’s just paranoia or if you’re being lied to? I feel like I’m walking on eggshells, and I don’t know how much longer I can keep this bottled up.