I understand your dilemma. When should your employer or the Plan have provided you the option to hop on COBRA, once you resigned?
The employer has 30 days after the event occurs to provide notice to
"COBRA Election Notice
After receiving a notice of a qualifying event, ... [resignation/termination is a qualifying event, and according to the DOL, that type of event, as opposed to divorce or other, is to be noticed to the plan by the Employer, not the Employee]
the plan must provide the qualified beneficiaries with an election notice, which describes their rights to continuation coverage and how to make an election.
The election notice must be provided to the qualified beneficiaries within 14 days
after the plan administrator receives the notice of a qualifying event." LINK
So, from the time of termination/resignation, you should have received your notice 30+14 = 44 days later, at a maximum. I realize what this has cost you.
COBRA continuation coverage laws are administered by several
agencies. The Departments of Labor and the Treasury have
jurisdiction over private-sector group health plans. So you may want to contact the DOL to file a complaint. I have to say I am not impressed with their enforcement measures, but it is a start.
If you need further information, we are told to
call (toll free) 1-866-444-EBSA (3272) to reach the Employee
Benefits Security Administration regional office nearest you.
Because I help people like you here, for a living---this is not a hobby for me---I sincerely appreciate your abiding by the honor system with regard to Accepting answers, by Clicking your ACCEPT button now. Feel free to follow up after, if you need clarification. An Accept also assures that I can assist you again. A BONUS is a wonderful way to tell the expert her time and effort are appreciated. I wish you the best in your future.