Have you picked up a digital thermometer with probe or temp gun yet? If your using an analog on the wall and its giving you the 91&84 temps the ground will be much warmer. I made this mistake with my first reptiles (leopard geckos) I hung my probe on the wall and it read 88 so I thought I was fine but then I read online what the proper placement of probe was then I found out I was over 100 on the ground. Make sure you put the thermometer probe on the floor of your enclosure.

If you haven't bought a thermostat yet you can get a lamp dimmer from Lowes or other hardware store but unlike a thermostat it will fluctuate with room temp so you will have to keep and eye on it. Its better then not having anything at all. I recommend when you do buy a thermostat that you get a proportional so it will maintain constant temps. They sell cheap on/off styles that you want to stay away from in my opinion. I had one of the zoo med ones and it would turn on at 85 and shut off at 95, way to much of a temp fluctuation for me. So remember proportional. You will place the thermostat probe on the floor just like the thermometer probe.

Good luck! Your not the only one who has suffered from what I call pet store syndrome. Most people probably have at one point or another.