Employer changed commission structure and won't pay me commission for month previous to change.

I am an esthetician in Texas who works for a dermatology office. I am paid twice monthly my hourly rate and once monthly a commission check based on sales of product and services. My employer informed me on March 10 that he changed my commission structure and has refused to release my commission check for February. The way I read the new commission structure terms I still met the new stricter terms for February. Can my employer inform me of the changed terms in March and then withhold Feb's check? What recourse do I have to get my Feb commission? He has let several employees go, some have left due to the toxic work atmosphere and I believe he is trying to force me to quit so he doesn't have to pay me unemployment. What do I do? - Is this your question? Add additional information