can't seem to handle sex with my boyfriend and it's affecting me 'F20'

My boyfriend is kind, patient, and I genuinely don't want to leave him. The issue is that whenever we try to have sex, I start shaking, shivering, and feeling overwhelmed. It happens almost every time.

One thing that might be relevant is that he's significantly larger than average, and I've wondered if that's part of the reason I'm struggling. I'm not sure if it's anxiety, fear of pain, physical discomfort, or a combination of things.

I love him and I'm attracted to him, so this isn't about not wanting him. I just can't seem to relax when it comes to sex, and it's becoming frustrating for both of us.

Has anyone been in a similar situation? What helped you? Was it more communication, taking things slower, relaxation techniques, or something else?

I really don't want to lose this relationship. Any advice would be appreciated