Why My Paycheck Gets Deducted When There's Extra Days In A Months (5 Tuesdays And Thursdays In March, June Etc.)

That is odd. how long have you been working there? Are  you paid by the hour? I never worked by salary,maybe they have to pay a base monthly ammount and just move the extra day to the next month?

You didn't say your position or classification. However, I can tell simply by what you wrote that you are or by law should be classified as an hourly worker. Someone in a position that is legally allowed to be exempt from the hourly wage laws just would not be asking you question. (Many companies do illegally classify certain employees as exempt, but even then, they don't just change your pay rate back and forth!) 

But then, I'm not sure you made a clear statement of the situation. You say they are changing your pay rate. But is that really so?

Under the hourly wage laws, even merely the federal basics, they cannot do what you are describing, it is a subtrafuge at best. They can't just supposedly change how much you make back and forth so as to effectively not pay you for hours worked.

You should file a formal complaint with the Labor Relations Board against the company. 

I would ask your employer to write out 3 months of your paychecks by earnings, and list every deductions separately. If this doesn't make sense to you there are labor departments that can help you. The Attorney Generals office of every state have people that can be very helpful to you. Communication between you and your employer needs to be improved. Sometimes seeing something written on paper can help.