The statutory bases for a court to grant a guardianship or de facto custodianship are quite limited. At present you have two problems: you are a minor, and the child has been with you only a matter of days. By and by, if the situation persists, you will be able to proceed under either the guardianship statute of the de facto custodian act (which requires 6 months of placement with you by the parent). The de facto custodian proof may be the easier because it is not necessary to prove the parent unfit only that the child has actually resided with the de facto custodian.
Best wishes for an outcome you can accept, and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.