I just replaced a flat on my rear road-bike tire. I had also tried to replace the rear axle, By removing the axle completely, to a quick release lock but realized the axle that had been installed with the bike tire wasn't hollow so put the old axle back on the bike, seemingly correctly. This morning i went for a ride and when I put any pressure while pedaling it felt as if the rear breaks were engaged. I checked to see what would happen if i pedal with the rear tire in the air and the tire seemed fine but came to a stop more quicker than usual but nothing too alarming. 

It seems the problem only occurs when im siting on the bike and there is weight. I also noticed when i pedal the rear derailleur seems to tug forward and hug the rear cog set. im not sure if that's the issue... 

Any ideas? I was wanting to save some money by not going to the LBS and learning and doing it myself. But I may have to go anyways. 

Here are some images of the bike 

   
![enter image description here][1]
![enter image description here][2]
![enter image description here][3]


  [1]: https://i.sstatic.net/pnFof.jpg
  [2]: https://i.sstatic.net/5c3t5.jpg
  [3]: https://i.sstatic.net/IQVe2.jpg