I'm new here too. I completely understand. I have 2 kids dealing with depression and anxiety, age 14. My son shut down and would just cry and say he felt sad and didn't know why. My daughter went through terrible bullying in jr high and ended up self harming. Both are in counseling and now on meds. I felt guilty and overwhelmed and scared and defensive, etc. But mostly I want them to be ok and healthy and happy.
I would recommend starting with counseling. My kids like and trust their counselors and i have felt like I have support and validation Im doing the right things, and so on. Hang in there!