Training for Time Trials

[Eden]

I mention the gasping part because I seem to have a tough time, either on the trainer or in spin class, pushing myself to what I think my actual max might be. Whereas when I am out on the bike on a really hard, steep hill, it is all I can do to keep from falling over and it seems like my lungs will just burst if I keep trying to get more air in.

I think you're not alone - I (and many others) find that indoors, on a trainer, feels much harder than the same effort outside. You've also been training for a couple of years now, and as you get more fit, it becomes harder and harder to reach your actual max.