I can relate to your situation. When I started Aikido I was terribly afraid - of messing up, looking stupid, being an inconvienience to anyone, rolling, falling, talking outloud, asking someone to train with me...... you name it. I still have moments of fear but it is much better now.
First thing to do - talk to your Sensei, tell him (or her) how you are feeling. Maybe he can suggest a senior student who will work with you one on one then you don't have to worry about who you are going to train with.
Socialize with your Dojo mates, once you get to know and trust them, you won't feel like they are judging you. I have found that most people who do Aikido are caring and compassionate.
One of the biggest things to do is tell everyone that you are terrified!!!! Once it is out there, it is not so embarrassing.
Most of all Keep Showing Up!! The more you are around your Aikido mates, the more comfortable you will feel.