First you need to secure your coverage through COBRA, which is continuation of your group coverage. I know COBRA is expensive but probably not as expensive as your treatment, if paid out of pocket!
Meanwhile you can look at getting an Individual plan. Without knowing where you live, I can't give you any more details, but no matter where you live, I recommend you get it through a licensed agent. A licensed agent, who deals with most of the leading insurance companies in your state, can help you pick a carrier/plan that matches your risk/needs. If/when you get approved for the individual plan of your choice, you can then cancel your COBRA.
To look at your options for individual plans, you can contact a local agent or go to a licensed online agency like (the one I work for) www.eHealthInsurance.com . You can call eHealthInsurance with any questions regarding plan benefits, eligibility or application process.
Most states offer low cost health insurance if you are employed. Also: UPS will pay for health insurance if you work for them for 4 hours per day/ five days a week. Shifts are late afternoon and evening.