Is my former employer discriminating if they pay retirement pension benefits to me differently then other employees?

As a general matter, the retirement plan is a legal entity separate from your employer. Your rights are limited to those set forth in the plan document. If you dispute the amount of your accrued benefit or the manner of payment, you need to pursue the proper defendants -- usually, the trustees of the retirement plan, not the employer -- and you need to know your rights under the plan itself. You should review the plan for how disputes are handled and resolved. You will have extremely limited rights to have judicial review of a determination by the plan trustees.