Oh, you poor thing!

As embarrassing as it is, I would ask the pharmacist if they could step in to a more quiet section of the chemist, and explain to them everything that you're feeling/seeing etc. It would be awful to put the wrong type of cream on and end up in a worse situation.

I hope they find something for you, and that it gives you some relief - quickly!

Oh, and an ice-pack wrapped in a light cloth in your knickers might give some relief from the pain.