I was right around 298 when I started riding again I now weight 265 or so. I still feel alot like how you feel specially when the roadies blow past me on the bike lanes. I am cruising right around 16-17 mph when I started i could barely hold 9 mph it is my motivation to keep losing the fat suit and eventually be a success story and ride as fast as they do it is my inspiration. Ride and ride the weight will come off and you will get faster with experience..
Good luck