Before, my bike was working fine. In every single gear (1-7) i could pedal hard and it would run smooth. When I went to go ride today, I pedaled hard on 3rd gear and it 'skipped' and caught again. Same thing would happen in every single gear. I have not looked into it in detail, but if anybody has dealt with this in the past, please help. The bike is completely stock and no modding was done to it at all.
How old is the bike? Could be caused by the chain/cassette getting worn down. Or it could also be low tension in the derailleur/cable not keeping the chain tight enough. I'd start by checking for excessive wear on the cassette teeth and chain, and if they still look good, pull the derailleur off and give it a good cleaning to make sure nothing's preventing it from tensioning properly. Then when you put it back on, go through the whole installation process of setting it up to make sure everything is lined up and the cable is tight. I had a similar problem with just a few gears skipping and doing a full clean/re-install fixed it.