How long can an employer hold your overtime pay before paying you for the overtime? If I work overtime on 06/03/12 can my employer not pay me for the overtime until 07/13/12, three paychecks later?

Pay has to be according to a published schedule. If they routinely delay overtime pay, they can, but they can't withhold pay discriminately.

If you believe this is being done, contact the TX Dept of Labor.