I am wondering if my employer has to offer me COBRA because the only have 10-15 full timers, but quite a few part time employees. I don't understand the requirements for this. Any help would be awesome.

Take the previous calender year. Add all full time employees. It's based on hours, so if you have 10 full timers and 20 part timers getting 20 hours per week, that equals 20 full timers, and the company would be subject to COBRA.

I think it's based on business days during the previous calender year. There is no official definition of "full time" but it's an agreement between employee and employer on what is "full time."