How to feel more confident

This may be long winded, so I apologize in advance. My fiancé and I have been together for 3 years, we have 2 kids via c-section. I know this man has seen about every “gross” aspect of me and still wholeheartedly loves me. Yet, for the absolute life of me, I am so shackled by my own insecurities that I struggle with our sex life. Some examples: I get extremely insecure about my body and get physically sick to my stomach if I try to be on top. Another is, we have a rather 🌶️spicy🌶️ sex life and there are new things I bought cause I want to adventure and explore, but I have yet to open the package cause I know when it comes down to it, I will completely lack the confidence to initiate it. This whole post is probably TMI, but I’ll add more. I know to him it probably seems like I find him unattractive, which isn’t the case. I want to climb the man like a tree any given day, but my own insecurities from past trauma and just my mind cockblock me. I can hardly even discuss the topic, I just get so anxious. How do I tackle this? (I am working on getting into therapy as well)