Me and my boyfriend have a child together but we were never married, can he just take the child and not give him back?

Is he on the birth certificate.  Typically, unless there is a court order in place giving you partial or joint custody or visitation, he can take the child.  The bigger question is if your child is living with him, is the child getting child support from you at all?

In Illinois, under Section 10-1 entitled "Kidnapping", kidnapping includes confinement of a child under the age of 13 against that child's will if the confinement is without the consent of that child's parent or legal guardian.  So it remains to be seen in your situation if it would be indeed kidnapping if the father took the child.  The best action to take is to take him to court to have the court help determine the rights of both parties, including visitation, custody and child support.
Consult with an attorney in your state.  You can try www.attorneypages.com.