Thermometer recommendations needed!

I've been using a Target brand BBT for the last 3 cycles. First cycle it seemed to work fine, second cycle I got lots of repeat temps, this third cycle my temps are all over the place and I'm having to temp 3-4 times in the morning and pick the temp that I get more than once as the temps vary by up to .5 a degree each time I test. I'm thinking I need to replace my thermometer for next cycle but I don't know what kind of thermometer to replace it with! Any recommendations are welcome!