Are you on a road bike riding at a leisurely pace? The slower you ride the heavier you sit in your saddle. And I'll suppose that some people just aren't built to handle the saddles we use on road bikes. And if you are on a hybrid.... well, I've never been on a hybrid that I've been comfortable on either. Though it's probably because I've never owned one and had to make it fit me. But even just trying them out at the shops they just feel wrong to me.
You might should try out what we use to call a cruiser bike BITD, that has a very slack seat tube angle and a very wide saddle. There are a few still sold, though many today aren't really what we'd have called cruisers back then.
Trek makes a line of them. Look at their Townies and some of the other bikes in their Electra lineup. Or consider a recumbent.