i have no idea how much of my retirement pay was nontaxable for each year. It is always the amount after the health benefits plan charges were taken out. What should I do

If you have no exclusion under the General Rule, then your pension is 100% taxable, which seems to have been the case for the last 18 years. See IRS Pub 939 for more information that may save you some income tax.

@opa21 

You will need to explain more.  Why do you think your income is tax exempt?  And why do you need to know your past information now?  

Social security is non-taxable if it is your only income, but is partly taxable if you have other income.  Clergy pensions can be excluded if they are a designated housing allowance.  Some states may give exemptions for retirement benefits.  But we need to know a lot more to understand your question.