Need help with a lawnmower problem!?

I have a Lawn Boy push lawn mower. Today while i was mowing the lawn i heard something weird underneath. I stopped and tipped it back so i could see that blade. There was nothing there but i think it might have been smoking a little (kinda looked like smoke was there). When i started it up again i noticed it was harder to push, even with the electric wheel turn handle pulled. I later found that when i pulled the handle the wheels wouldn't turn, and i was not able to make the lawnmower wheels turn backwards when i pulled on it. When i pull on the handle, though, the engine noise does change slightly. It drops (i think) as if it suddenly lost some power. I was wondering if maybe it could be something caught in the wheel mechanisms or something that i could fix at home, or if i might want to bring it in to have it looked at. I'm only fifteen and started using this lawnmower when my dad moved out so i don't know anything about lawnmowers.