Check with you local health department. I know most counties have one. Ours offer all services, including family planning, which is on a payment fee according to your income and number in your household. They also offer visits for the children. If you live in a larger city, a lot of times they offer a complete line of care.
Also every state has insurance for the kids that fall in the cracks, they ones that cannot be on Medicaid but can't afford to purchase insurance. Check with your state Dept of Health or Social Services. A lot of schools should have this info also.
Good luck!