So, i have an old Haro i got from a cousin, and it worked great until one day when i was peddling, and all of a sudden my pedals started spinning as if a gear slipped. im not sure what exactly it is, but what happens is, when i pedal with any decent force the crank or whatever it is that is inside where the crank is, looses all tension and no matter how hard i pedal, i wont go anywhere till the gear or something catches and i can resume pedaling. any help would be great concidering i spent the past hour and a half trying to find out what was wrong with it.

Your problem is likely in the vicinity of the rear hub instead of the bottom bracket.

Freewheel is either shot (broken pawls or wasted pawl springs) or just junked up. If just gunked up sometimes you can flush 'em out and they start to work again. If you have access to a parts washer they're pretty good for flushing them out. Just remove freewheel and aim the stream of fluid at the cracks. Wear gloves and put the freewheel around your finger and spin with your other hand.

If you don't have a parts washer sometimes you can just dribble some mineral spirits in with a drip bottle or you can blow a whole can of WD-40 through it.

Might be easiest to just replace freewheel if you don't wanna mess with it.