Last year I was on FMLA / disability benefits for 12 weeks. Do I need to file taxes on these funds I received?

Payments you received from a disability insurance policy that you paid the premiums for are not earned income. It does not matter whether you have reached minimum retirement age. If this policy is through your employer, the amount may be shown in box 12 of your Form W-2 with code "J." Then it will be reported as income.
If you retired on disability, benefits you receive under your employer's disability retirement plan are considered earned income until you reach minimum retirement age.

Thank you!