Have you actually had someone measure the distance between your sit bones or did you just try saddles without that measurement?
If it is the latter you should have a LBS measure your sit bones by having you sit on foam. From there you can find a seat that actually works with your body vs. putting pressure in places you do not like.
I would recommend a short nose saddle along with a cut out to alleviate any pressure on soft tissue. After making the switch to the proper width saddle that is also short nose with a cut out, I can do 50 miles at one stretch with basketball shorts. Before that even when I had on a padded bib, I never could get comfortable on long rides.
Certainly riding shorts or bibs help, but make sure it is not being used to cover up an incorrectly sized saddle. Also have a bike fitter eyeball if everything else looks right and usually if you buy the seat from them they will help set the right position and tilt for the seat.
Here is GCN's detailed explanation of it that elaborate on sit bones.
Hope that helps.
Here is a DIY method to measure your sit bones where you can - 1) Find a flat surface, 2) Put a wet paper towel on the surface, 3) Put a piece of paper over the paper towel, 4) Sit on all of the above, 5) Measure your sit bones from the water marks on the paper.
It is pretty much a similar process with memory foam many bike fitters use: