When I got my first road bike, I was riding with my hands on the straight part of the bar because I didn't have the core strength to ride on the hoods. When I did ride on the hoods or in the drops, my arms would start hurting from using my arm muscles to hold me up. After I built up my core strength, I began riding the hoods and started sliding forward every time I got on the hoods. The bike had an OEM 110 mm stem that was replaced with a 90 mm stem and that solved the problem and I didn't have to do anything to the saddle. You may want to try a shorter stem and see if that makes a difference for you.