Does he have any formal arrangement with your school? For example, did you find the job through the university's placement office or your department?
Lack of payment will not affect your status in your current situation (not the case under all OPT programs). I am, however, concerned about the legitimacy of an employer who is delinquent in his payroll obligations. Since it sounds like you are on a required component of your program, I think you have good reason to worry about receiving credit should your employer close his business (for bankruptcy for example) prior to you completing the term. If this is a possibility, go to speak with your department chairperson to determine the possible consequences of something like this occurring.
