If your charity care has been your primary care-giver until recently, the pre-existing clause time limit might just be starting for you as you didn't use/have the April insurance coverage until now?

I would call the insurance company back and ask them specifically about your April insurance, how long it's pre-existing clause time limit is, what it covers, and when you, specifically, started primary coverage with that insurance and check that, "So I am now completely covered, even for pre-existing conditions?". But it sounds like you most need to know when you were covered by this insurance and then add how many months to that date, not the date you bought the policy to know when pre-existing conditions were and/or the exact month you had care last versus whether that would count during the period (i.e., if it's a six month pre-existing clause and you had care eight months ago, you should be clear).