Teens in foster care have the right to seek confidential services for reproductive health from contraception to STI treatment; there is no lower age limit. Your social worker is responsible for making sure you have information on birth control.
If your social worker is uncomfortable helping you with birth control, they are legally required to connect you with Planned Parenthood or some other family planning clinic that will provide this information to you.
In the state of California, all teens in the foster care system who are in out-of-home placement are automatically eligible for Medi-Cal which is free healthcare that includes birth control. You do not need your parent’s permission to get birth control in the state of California and physicians are not allowed to tell your parents if you have accessed birth control.