As a fellow Clyde -- you need to get your sit bones measured. Just because you look big, doesn't tell us how wide your sit bones are, and that is the key to saddle fit. If you are lucky, you will be in that 140ish range and can find many options to try. But for me, at 154 -- there weren't many options. I have a Selle Italia Max Flite and a Brooks B-17. Those both work
pretty well.
You can do a decent job at home measuring by sitting on a bag of brown sugar or something. But a good LBS should have a method and they may be willing to let you demo a saddle or two as well.
Of course, as others have mentioned, you will need to build up your posterior fitness.