Hello Nita,
Given that you are not tired, I think that there may be two things for you to look at.
Lane dressing break down; as more games are rolled, the oil patten changes. If you are still putting the ball down in the same position, but the ball is acting differently, you need to start adjusting.
If you are trying to adjust, are you doing it correctly? These is a wealth of information on the web about different adjustment systems. Or you might consider working with a coach for a few lessons. They would be able to not only see your style, but help you focus on the best adjustment system for you.
The other thing to consider, is if you are trying to adjust correctly, then you have developed a mental block concerning the 2nd game. Relax and roll one ball at a time.

Lon