Insecure help

For the past few days I've been very insecure in my relationship

I really dont know why, before this I had so much trust in him, and I would never think he would ever cheat on me

But this week he started a new job, and I haven't really seen him much, and for some reason I get this feeling that he's acting different, and I think something is going on.

I asked him about it, and he said nothing is going on, he would never cheat on me, he jokes that one is enough trouble. He says I was spoiled with attention because he was home for a few months off work due to covid, and now that he's back at a new job I cant handle it (he was going crazy now being able to do his regular job, so for the time being he found something else - temporary)

Deep down I know he's not cheating on me, but sometimes I get this feeling that's hard to ignore

Can anyone give me some advice to feel more secure? I'm tired of feeling this way