Feel guilty about having another child

I am pregnant with my 3rd child. It was kind of an accident but I want to keep it. Problem is, I feel guilty about it because of my other children. I have a 12 year old boy and 9 year old girl and we are a very happy family. I'm worried that the new baby will take my attention and love away from my other 2. I don't want to break up our bubble of happiness. I feel so guilty on my other kids, but also feel guilty about the baby. What if I don't bond with it because of these feelings or what if I lose my bond with my other 2? Anybody in the same position or feeling the same? Sick of feeling sad and guilty every time I think of the new baby's arrival.