Yes! Prior to the Affordable Care Act, health insurance companies could deny you coverage or charge you more if you had a pre-existing condition. However, under the new law, insurance companies can't deny you coverage or charge you more if you have pre-existing medical condition, such as back pain, diabetes or cancer. Also, once you have coverage and have paid for any deductibles, co-insurance or co-pays required, your insurance company can't refuse to pay for treatment for your pre-existing medical condition.
The only exception to this is if you have a grandfathered individual health insurance plan directly through an insurance company. If you have one of these plans and it doesn't cover pre-existing medical conditions, you may change your plan during open enrollment and switch to a Marketplace plan that covers pre-existing conditions.
You can find more information on HealthCare.gov: https://www.healthcare.gov/health-care-law-protections/