FWB Felt Me Opening Up

Today my FWB came over and I’ve hooked up with him a couple of times but have always had a hard time cumming when hooking up with someone new. Like a mind over matter thing. This is like the fifth time we’ve hooked up and I know it takes me a while to orgasm or not at all in the times we’ve done it, he’s so patient. Today I was in doggy and he was fingering me from behind and maybe it was because I trusted him so much since he’s gentle and tells me I’m beautiful, or maybe because I wasn’t facing him, but I felt my whole vagina relax and my uterus too – it wasn’t an orgasm(?) but it was very very pleasant and it felt so intense and significant in what we were doing, and I got sleepy after. After when we finally took a break, he said “I felt you open up for me” and it was really hot and I felt proud of my body for doing that (weird I guess but I’m a bit insecure and I think it’s because I finally trust him and have been consistant with him?) has anyone experienced “Opening up” before and how did it feel for you?