the best advice is always honesty - as one who has hired lots of people, I'd much rather have someone be really honest - especially about what they're not good at - then have them not be honest, discover that the hard way, and have to fire them - especially if the trait of themselves they weren't honest about is one that's critical to performing the job they were hired for.

Buck up - be truthful, honest, and up front - let them know you're not a really open 'people person' right away with strangers you don't know - it'll be a lot better for you and your potential employer.

As to the eye contact thing - that's usually read by almost everyone as a sign of deception - is it something from childhood? However you got it - try to work on it - if you're being truthful with someone, you should be able to look right at them, without any fear.

good luck!

OK, well, one thing might be, get practiced at talking to others again, by forcing yourself into a somewhat social hobby - its something that constant lowlevel practice WILL enhance your skills.

Alternatively, look for jobs where you work solo or (ideally) from home, where you can limit social interactions to email & msg'ing.

And when putting together a resume, don't comment on your communications skills at all, but use words to describe your close focus & concentration on the task, and how you can ignore social distractions.

I'm pretty quiet too, and that's not necessarily a bad thing. Communication doesn't require one to talk endlessly. If you know how to convey your point, that's ten times better than having auditory diarrhea.
As to speaking not loud enough, that's a problem I cannot solve myself either. I just speak too loud when I do speak. We all have our quirks. Just remember that when you're at an interview, you're there because those guys NEED you. Not because they feel like interrogating you.

PM me .. let's talk it out ^^ together :)