Listen OP, they should not take your kids away unless you have been hospitalized or have a record of some sort stating you can not. I wish to think the state is not so barbaric in their thinking because if you are suffering from an illness as long as you are been treated for it (just like diabetes, aids, cancer and so on...) you should have all the rights to keep your children.

Now, I don't wish your little one to be subjected into some sort of medication at such a young age. Being a previous suffered from depression I know how hard this can be and the place you are in (I'm also a father), but perhaps taking him first to a therapist to get an evaluation should be the best thing and to see how helpful this therapist can be as to not subject the little one to medications at such a young age.

Don't beat yourself down b/c you want to blame yourself you passed this down to one of your sons. It is not your fault, neither could you have prevented this. You seem to be a great father/parent by your objective and willingness to help your son.

I really wish you and your kid experiencing these problems the best and make sure you keep yourself checks out b/c if you are not there as one of the father (specially a father figure), then who will.

Good luck man.