Hear me out please.

Today I noticed a thing with me. I feel like I'm unable to speak when I'm being seen when I'm vulnerable. I noticed it today only as I was sitting with my friend and I was just thinking and thinking and we both were quiet for like 30 minutes. I became visibly sad and he asked me if I'm okay, I said yes and nodded and we both became quiet again. And then, he asked again, but I still nodded yes. There came a point when I wanted to speak but the words just wouldn't come out of my point, i tried and tried but I don't know what was wrong with me, my jaw was like kinda shaking, I could say things like 1-2 words but I couldn't say what I wanted to say and what was actually bothering me. I noticed it first time only because I hadn't been put in this situation ever. I've never been seen vulnerable. Is there someone who has felt same and I wanted to know howd you overcome it