Your fitter will be able to see your body position and movement on the bike. They can also take into account things like your chamois and saddle. That’s probably the best way to find a solution. Have you measured your sit bones?
I stand to relieve pressure, improve blood flow, stretch my back and use pedal strokes to stretch my legs often on longer rides. Always standing or lifting yourself off the saddle over any bumps helps too.
congrats on getting into a healthy exercise like bicycling!!!!!...hoping the fitter finds a solution for you.
‘The negative feelings we all have can be addictive…just as the positive…it’s up to
us to decide which ones we want to choose and feed”… Pema Chodron