I felt this way as well. Everyone (most of whom are younger than me) all seem to have such insightful comments and questions, and they know exactly when to speak. I remember my first year in university, I was sitting there listening to someone say something in my English class, and realized that it had completely passed me entirely, and I could not come up with something intelligent to say. I thought to myself, "I don't belong here...I'm too stupid!" Of course, I am not really stupid, and I have better grades than most of those students. I just have trouble speaking, and I get accommodation for that in school. It sucks sometimes, but that is the way it is. In labs where you are working with a partner, I would talk as much as you can. That doesn't mean you have to engage in small talk or outside conversation, just put in your say as much as possible. I worked with a girl in Chem lab last year, and I spoke little, but DID a lot (and spoke when I could). She kept on asking me to partner up with her, so I guess I didn't scare her off. Just be sure to do your share of the work, and you should be fine.
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Diagnosed with classic Autism
AQ score= 48
PDD assessment score= 170 (severe PDD)
EQ=8 SQ=93 (Extreme Systemizer)
Alexithymia Quiz=164/185 (high)