I work for a rent-all place we deliver party supplies, ok heres my question, we work more then 40 hours a week, but we dont get overtime. insted they take our over hours and bank them untill we have a short week. my question is can they do that or should they be paying us for the overtime?

They should be paying you overtime for all hours you work over 40 in a week. http://www.michigan.gov/documents/MWPosting_89313_7.Optional.pdf

on there it says jobs only open 7 months a year would that be in that catagory? they are a summer rentall i think they are only open 7 months

That changes the picture. If a business operates no more than 7 months per year, and meets the other eligibility requirements, there is an exemption for overtime. You can read about the conditions at: http://www.dol.gov/esa/regs/compliance/whd/whdfs18.htm