Yah, relax. You cannot listen when your are stressed to the max. Ensemble playing is first about listening and is ALL about hearing. This cannot be accomplished with anxiety clouding the senses. Listening to CDs is NOT the solution here. You need to go into the ensemble NOT thinking "this ensemble does nothing but worsen my ability to keep time" to I am going to key into the most solid rhythm player in the ensemble and OUTLINE his/her patterns, and on each cycle, I will then add to the complexity of my lines.