looking for a pair of shorts with a wide chamois, I cant seem to keep mine under me if they move even a little
OK, most people, regardless of weight, have similar sized sit bones and therefore need similar sized chamois. What do you mean by "keep mine under me" even if they move a little? What kind of saddle are you on and what kind of bike?
My shorts are pretty damn snug - they don't move at all (road bike bibs) so maybe it's just my frame of reference is different.
Bike shorts should not shift around at all while you ride. They should be snug.
That prevents chafing as well as wicking moisture. They also prevent "flappage" if you have large legs.
Check your saddle height, saddle, and overall bike fit. Something doesn't sound right.