This is a very normal feeling. I've been there. What I can tell you is that those who really know you know that you are not a bad parent. Those that want to judge you have no clue what it's like to have lived through what we have. I say to them, live one week in the chaos and drama we have lived and they would run screaming.
It's easier said than done but do try not to put importance on what other people think of you. Their opinions do not matter. You, me and all the other moms and dads here have done the best we could. Of course we have all made mistakes, done and said things we wish we could change but in the end, our adult difficult children have made their own choices of how they will live their lives. That's on them, no us.
Hang in there dear lady!!