More than likely just irritated the area from the increased volume of riding in a quick time span. One could assume that some swelling may have occurred not only in the perineum but possibly also compounded by swollen legs, etc. The tell tale IMO is the fact that taking down shoulder straps offered some relief.
Take a break for a moment, let yourself recover, and see if the issue resolves. If it doesn't you may want to consider different riding shorts, possibly a seat or position change, and if those don't help, ask your doctor about it.