Sounds like you aren't using a UTH, which is what most people here suggest. Since balls hide 99% of the time, over head heat doesn't work as well as belly heat. Heat lamps are fine for raising the ambient temp, but in my opinion shouldn't be used for a hot spot.

I would get yourself a UTH and a thermostat for your hot side and use the lamp to heat the enclosure (overall) to the low 80's.