How to control fears...

I worry constantly about my relationship with my SO. I'm terrified he will get bored with me and leave. I'm 23w and I don't know if my insecurities are tied to pregnancy hormones, insecurity or what. My SO and I talk about my fears, and I believe he's getting frustrated. He doesn't know how to get me to believe what he says as that all is well. I hear him, but can't seem to process it. It's like I get the rational side of things, but emotionally I can't figure it out. I don't know what to do. I love him so much. I'm afraid my worrying will push him away...but I can't get myself to stop worrying!!! I feel like I'm going crazy!!!!