So I am continuously bringing up the rear on my training rides...and while I know I've made huge progress, I wanna pick it up. How do I get faster?

Is this a case of continuing to work out in the gym (with additional cardio work as of last week?), and just slowly getting better? or is there something I can do to get to that next level?

OTOH, I'm REALLY tired after this week of more cardio. Can't wait to feel rested again.