Working to Gain Confidence

I've been at my company for over 8 years. I interned here, did my senior project here, worked in various places in the organization, etc.

But still I feel like I'm invisible. It could have to do with my personality. I must admit I'm a bit of a Negative Nancy, but I always thought my smarts and good work made up for it. The benefit of being negative is that I'm conservative and take a lot of pains to ensure that if something is done, it is done right. However, perhaps it makes it seem like I don't have enough confidence in myself, which is something I do sometimes have an issue with.

I'm also not the type to go bragging about the things I've accomplished. I mean I tell my boss during one on one sessions about what I've been up to, but he's not much of the verbal type to share it with others.

I try to build my confidence by listing the things I've accomplished. However when I'm not EVER recognized by managers or peers for knowing what I know, I get frustrated and end up second guessing everything I thought I knew about myself.

Take for example ...

My company has been putting together a series of internal classes to teach the engineers about the basics of our technology. I've gone through trainings like this before (too many to count), but it is no secret that I LOVE to learn and LOVE anything that is school related. A month or so back, I even offered to one of the upper management engineers who was going to plan these classes that I would love to help out in learning about and then teaching one of the modules. I feel like I have the capacity to do this and to do it well.

Recently, I heard that an email went around polling people who were interested in taking these new classes. And lo and behold, my name along with a couple of other engineers (no rhyme or reason so it seems) wasn't even on the distribution list. Now maybe it could have been an honest mistake and it just slipped their mind to include me (although this isn't the first time something like this has happened.) And obviously my interest in helping out was ignored since the planning of the classes is going on without my knowledge and with one of the organizing engineers having less experience then me. It could be possible that they think I'm too busy, but still what would be the harm in asking...

I feel like work is a lot like school. If you aren't in the "in" crowd, well sorry,  tough luck. You can stay out there and look at us make ourselves look good and you can just look like an outsider. Seems real mature, eh?

It's not that I'm looking to move up in the company to extraordinary proportions or anything. The Hubs and I are in the process of trying to grow our family, so added work stress and responsiblity is not what I'm looking for. I also don't really want to look for a new job because I don't want to start at a new company from scratch with regards to benefits.

So it seems I need to find another way to build my confidence in the workforce and I need to prevent events like this from setting me back.

Have you ever dealt with self-confidence issues at work? 
Do you have any tips on how to gain self-confidence without outside influences?