Losing the ability to speak

Hi all. I hope I can get some advice on this.
Today my gf and I were doing some heavy making out/grinding/touching/etc and I ran into a problem where I was really, really struggling to speak. The more aroused I got, the more trouble I had forming words. It’s not that I just couldn’t get the words out, I just seemed to lose the ability to turn my wants into actual sentences.
Thankfully, she understands my body language pretty well, but it feels unfair to make her rely on just that. For example, earlier, she wanted me to try biting her. I just kept moving away when she pushed me to her neck because I physically could not form the thoughts to describe that the idea of doing that made me nervous.
I don’t/didn’t feel uncomfortable with her. I often do have troubles speaking to people I’m uncomfortable with (like strangers) in day-to-day life, but I haven’t had this issue with her. I’m completely comfortable and I’m not scared of her, I just feel like I can’t think properly and that’s kind of scary.
Is this a common problem? I’m very inexperienced so this is honestly something I’m just now running into. Does anyone have any advice on how to fix, or at least aid with, this?