Overtime Question

I am an IT engineer working for a small company in Toledo. I feel we are getting a bad deal as far as overtime is concerned. I will explain how my compensation works. I am a non exempt employee. I get paid $22 and some change an hour. Also, for every billable hour over 80 per month I receive an additional $15 per billable hour which is paid out in the last paycheck every month. So, if I work 40 hours during a regular work week and then work an additional 10 hours on the weekend I will get paid an extra $150 assuming I already have 80 hours for the month. I think it's unfair that working on the weekend gets you only $15 per hour. Another thing that I think is wrong is that it takes about 50hrs per week including driving, picking up equipment etc. to reach 40 billable hours. The bonus is nice but I think we should be getting overtime ANYTIME we work over 40. My assumption is that the bonus is outside of the overtime if the company wishes to do that. Am I correct on this?