Hey Gale,
I am in a similar boat as I am trying to desensitise myself from feeling self-conscious at the gym too these days. Some ideas that made me feel a bit better about it:
Observe other aerobic classes, or people filing in and out of other classes while waiting for mine to start. I mean if you take a look, there are so many different shapes and sizes, it is quite amazing! And they all come here to exercise. I may be the fattest chick I have seen there but certainly not the only overweight one, neither the tallest, neither the most ugly, neither the most sweaty and neither the slowest learner in my dance aerobic class. Realising that made me feel much less like an outlander.
I also noticed that I feel far more comfortable in aerobic or pilates classes than in the weight and carido rooms so I try to focus on getting my exercise in those ways but I really think that just going there regularly is the only true way out of feeling out-of-place. Habits are comfortable. Period.
My expectations were far worse than reality in terms of how people treated me, i.e. normal.
I even had one of the buff trainers come up and talk to me after one class to see how I liked it and to encourage me to come again, go figure. Other times people being friendly in aerobic class or at the reception desk. Not über-friendly, just normal and it is a very nice feeling!
I also keep thinking, if I felt very strongly about being fit and exercising and saw someone new making and effort, I would probably have a very positive and encouraging attitude towards them for making what I considered to be a valuable change to their lives, so why should the people at the gym feel differently?
And honesty, every woman who is thinner than you should like you a lot for being able to make that comparison in her head and applauding herself afterwards.
Make it a habit and enjoy the health benefits and social aspects of it too. Life is too short and can be too much fun to do otherwise.