I too struggle with this. In fact, I have to greatly commend you for opening up like that, and for joining WM. One of the reasons I joined (just recently) is to help me get past these feelings. I'm pretty quiet in chat too, and when I do respond I think of how stupid I probably sounded, but I'm sorta forcing myself to ignore that feeling and realize that these people have no idea who I am (sorry everyone if that sounds rude). I'm hoping that by continually telling my "flesh" to shut up, and allowing my soul to be who God's created me to be, I'll eventually be able to carry that reaction into face to face interactions. I'm an awkward work in progress, but I completely believe Philippians 1:6 "being confident of this, that He who began a good work in you will carry it on to completion until the day of Christ Jesus."
LOL, it's even hard for me to hit Submit Reply on this, but here goes...