another thought. Does your bike have multiple gears?
make sure it's in the easiest gear before you get on the bike. easiest,
wheels spin with the least amount of work.
another thought:
pick up the front of your bike. Spin your wheel with your hand. Does it
spin freely?
pick up the back of your bike. do the same thing.
if the wheel doesn't just keep spinning,, something is wrong.

when i got my cross, the first day i rode it, a brake pedal was stuck.
I got on that bike and rode 10 miles (VERY SLOWLY) my husband getting irritated, scolding me even..
i finally threw myself down on the ground and panted, my legs were screaming.
needless to say it took a while to figure out what was wrong.
I always check first now