Jezebelle - I worry about loose skin as well...so far I've lost almost 50 pounds (I am at approx. the same weight as you) and it hasn't been a huge issue yet, but I can tell that once I lose another 50, it's probably going to be an issue. However, I've been psyching myself up on that future, so to speak: at first the loose skin issue was such a de-motivator for me, but in time I learned to accept that it's a very real possibility, but that I shouldn't let it stop me from becoming healthy.
I lift weights regularly at the gym and having the right trainer made all the difference. My trainer took me very seriously and pushed me and is great at letting me know how impressed he is with my progress. He also enouraged me to lift heavy weights instead of relegating me solely to light weights. He consistently gave me new weight lifting programs every 6 weeks-ish. I too have been self conscious about going to the gym, but if you force yourself to go in the beginning, and stick with it, you become more confident. For example, I've become so comfortable with the weights in the gym that I go into that section with *a lot* of confidence - because I know that I know a lot about weight training, probably at least as much as any of the people in the weights area...knowledge is power!

If you can, spending some time with a trainer at the beginning is very helpful in becoming comfortable with all aspects of the gym.