Another vote here for Aerotech designs. I've been as big as a 46" waist and their 3xl bibs fit me very well. The thing I like best about bibs is that my butt crack doesn't hang out anymore.
What I've been doing lately is a pair of cycling shorts underneath my bibs. Skinny riders will scoff at this idea, but as a big rider, the extra padding definitely helps me stay in the saddle longer.
Keep at it and it'll get easier. I'm down almost 70 pounds and can ride 45-50 miles pretty comfortably.