I suffered a similar PITA on my 1st decent ride out on my 67 plate lowered GS on Thursday which has a thinner seat than yours. I had by then been riding for well over 2 hours having ridden from Worcestershire out on the A44 to Builth Wells, on though Llandovery and down to Camarthen as the Llandovery/Lampeter road was closed. It wasn't until I got to Lampeter that it got uncomfortable so as others have said some of your discomfort may just be down to not doing any miles over winter. Cycling undies help as they come with some padding and crucially no seams to create pressure points (Aldi do them for about a fiver on special deals from time to time). I also have a tourtecs gell pad off ebay which helps too for not a lot of money compared to the alternatives, but had neither on Thursday