I'm not at all qualified to offer advice for this, but if you want to keep writing, I will keep listening. I think every single emotion you are feeling is 100% valid. There ought to be no shame in our society to admit that you might regret having a child, especially when it's clear that you are doing so much to make his life the best it can be.
Admitting how hard this is, and how bad the timing in your life was for all this does not make you a bad person or mother. I promise you that much.