Do cottage-cheese thighs and doughy behind have you recoiling from your own reflection in the mirror? It’s cardio time, bubble-butt. No can do, you say. The price of gyms these days! Stop right there. You can get fit on the cheap at UIC’s Chicago Circle Fitness Center — a nifty under-the-radar gym that has all the perks of a schmancy health club at a fraction of the cost. Sweat it off on state-of-the-art machines. Buff saggy biceps in the weight room. Butterfly-kick your way to a leaner you in the 25-meter, six-lane swimming pool. Need more help? Personal trainers are just $32 an hour — subterranean prices for some serious one-on-one attention. And when you’re all repped out, hit the sauna and dream about how gorgeous you’ll look in the slinky Marc Jacobs number you saw last week. You can afford it now. UIC’s Chicago Circle Center, 750 South Halsted Street, at Polk Street (312-413-5160).