I started having a problem today, I dont know if it would be considered the chain skipping or slipping. Either way, if I put too much force on a downstroke the pedals skip forward a bit, if I put enough pressure the opposite way it skips/slips back into place. Very annoying. Is this due to poor chain tension? How can I tell if my cog isnt tight enough and could that be the problem? I did recently get a new chain and cog. The cog was put on by someone at a bike shop, and I know chains need to be worked in. Any ideas? I wanna get this problem fixed now before it turns into something much larger.