Then don’t add to the pileup.
Focus on taking care of your other children and let this child be the one that has a future with a mother and father provided through adoption. You can be part of the adoption process and select the type of parents with the birth mother if you’re in good graces with her. You need to get along and while it might be a bit of a stretch, respect her and her wishes. It’s important you do understand that she wants to do what is best for the child and you should respect that.
Your role and responsibilities are to see to it that she has your support and that the adoptive parents know you’re a good guy to share with the adopted a child later in life. You’ll find you grow up really fast and mature through this process.