it sounds to me like you are NOT entitled, unless your prescription exemption form is because of low income
•You receive Income Support or Income-based Jobseeker's Allowance (not contribution-based)
•You receive Pension Credit Guarantee Credit.
•You receive Income-based Employment and Support Allowance.
•You are awarded Universal Credit
•You are entitled to, or named on, a valid NHS tax credit exemption certificate.
•You are named on a valid NHS certificate for full help with health costs (HC2). People named on an NHS certificate for partial help with health costs (HC3) may also get help.