Why does it hurt so much when I ride without stirrups? (Kinda embarrassing question)?

Riding bareback can be more uncomfortable, especially on a horse with prominent withers or a narrow back. However, pain (rather than discomfort) might indicate something medical such as a cyst or PID. It wouldn't hurt to talk to your doctor, yes it is awkward, but doctors have seen far worse and feeling better and making sure you are healthy is worth a little embarrassment.