Unfortunately, retiree plans, such as your father's plan, are not included in the ACA-under-age-26 requirement.
On a brighter note, health insurers will NOT be able to deny you based on a pre-existing condition if you shop for health insurance elsewhere. Also, if you cannot afford health insurance, you may qualify for financial help through Medicaid. Reach out the the NJ Dept of Human Services to see what your options are: http://www.state.nj.us/humanservices/
Hope this helps!
This information is for informational purposes only and is NOT legal advice.