Getting over fear of being cheated on? So lost

I am in a loving relationship and my partner has not given me a single reason to be worried about his loyalty. He is honest, reliable, loving and so so kind. I know he would do anything for me and wants to give me the world. That being said, lately I have just been overwhelmed with how much I love him and have been so fearful and paranoid about him cheating out of thin air. How can I get over these insecurities and fears of being cheated on? I know it stems from my past and worried about being hurt... any tips? But also if I’m this worried about it is it my gut telling me something or am I just insecure?? I’m lost