stepmom fulltime, help
I am a step mom to a 7 yr old boy. His bio mom was sporadically in his life until about 4, and by now he wouldn't even recognize her. She simply wants nothing to do with him. As this has been an evolving situation, I didn't 'sign up' to be the one and only mommy to this child, I haven't even had a chance to have my own child yet. But I have been married to my husband for a couple years and I am not sure how the family dynamics should keep progressing. While it is unfair to this boy not to have a mom, it's not my fault and I feel this huge weight of being his parent. I don't know where to draw the line between fair to this boy, and fair to myself. Am I supposed to carry on like a biological mother would, or start stepping back and letting his dad (my husband) handle more of the parenting.
I also don't know what is an appropriate age to tell him the truth. I do not want him to grow up not knowing the truth, but at the same time I don't think he will understand the truth right now, because his first question will be 'where is my real mom'. I am not about to tell a little child his mom doesn't want to be around, so I have let him believe I am his real mom.
I'm confused, and never saw myself being in this position. I would really like to take a step back and not take so much of this parenting on, but I don't want to harm the child either.
Suggestions and comments would be appreciated :)