Why do I feel angry about sex?

Soo for context im gay and in my 20s. Iv been offered sex multiple times already and every time I regret it. But I get mad i hesitant and second guess myself. In a way it feels like im betraying myself just even considering the thought of it. Also I noticed that any time I think about sex or if it's brought up I get this tennis physical feeling. It's like my body goes into fight or flight mode idk why. If anyone juat has some instances please let me know lowk lost in all of this.