Okay, the under-20 thing is important and I should have caught that. Technically, then, that was not COBRA, but state continuation. It amounts to the same thing in terms of the coverage, but it's important for the reasons we just discovered; it makes a big difference in terms of the definitions.
Here's another very important thing to consider; it is possible for the CONDITION to be covered, but for the specific treatment you (or your doctor) wants, to be not covered under the plan. Just because the treatment was denied does NOT mean, just of itself, that they are calling the condition pre-existing (unless, of course, they told you that they are.)
Here's the deal. If I am understanding you correctly, you have access to a group health insurance policy from your employer, but your Fortis salesman convinced you not to take it. While I'm not blaming you for believing him, that was a sales trick. As an employer, I can tell you that whether an employee has their own insurance or not makes no difference to me in the least. Sure, it's cheaper for me if he does, but he won't get a higher salary or a bigger bonus package by virtue of the fact that he's not taking the benefits. No leverage there.
You need to find out, first, when is the next open enrollment period. You want to join the group health plan at an open enrollment period if at all possible, even if they'll let you on sooner, which they may or may not be able to do.
Also you want to find out whether the treatment you want is even covered. As I said above, even if the condition is not considered pre-existing, it does not follow that every possible treatment for the condition is automatically a covered benefit under the plan.
Here's why I'm pointing you this way. It is to your benefit to get onto a group plan. You do not want to go onto another individual plan, because HIPAA does not apply when you go from one individual plan to another individual plan. It does count if you go from a group plan to a group plan, or an individual plan to a group plan.
Once on the group plan, any creditable coverage you have had before will be counted. That will include the time on your current individual plan and also the state continuation coverage. If you have been covered on some creditable policy for 12 months or more, with no gap in coverage for 63 days or longer, they CANNOT count any condition as pre-existing. If you have a 63 day or longer gap, or if you had less than 12 months creditable coverage, the maxiumum length of time your condition can be considered pre-ex will be the difference of your creditiable coverage and 12 months; so for example, if you had eight months of creditable coverage, the maximum they can consider a condition pre-ex is 4 months.
Clear as mud?