One aspect of anxiety is rumination. It sounds like that's what is going on here. You are ruminating on these things in the past, going over and over them in your mind and you are feeling more worthless and ashamed and upset.
Try breathing in and thinking about all these things in the past, then slowly breath them out. Maybe think something like "I am releasing myself From the past" or "I'm breathing out the past." You can also do this by lighting a candle and concentrating on the flame. Think about all the things in the past, then blow the candle out. Those things are now gone. Each time they start to upset you again, do this again. You can also try tending up all your muscles and then releasing them. I do this by thinking "I'm so anxious about x issue in my life" and tensing all my muscles up, and then thinking "and now I'm letting it go" and relaxing all my muscles again.
Lots of other people have written it a lot more eloquently than this, but anxiety is either about the past or the future. It lived in our rumination over the past, and our fears for the future. But when we are centred in the moment, when we are just concentrating on our breathing and the present moment, we are released from anxiety. When you are practising mindfulness you are in the moment. So whatever tools you use to get there, try to find a way to be in the present moment only. Release yourself from the past, which you cannot change, and the future, which isn't here yet, and instead concentrate on right now. What can you do right now to feel better? Yes it's important to have a plan to get out of mental health crisis, like going back on medication and referring for counselling things like that, but in crisis it's most important to look after yourself right now. To find a way to feel a little bit better right now.
I hope you can find some peace in the here and now and that your crisis passes quickly. I know how it feels to think nobody cares and nobody has been where you are. I may not know you but I do care that you feel this waY, and I have been there myself. I am sending you healing energy, who know if it will get to you but I hope that it helps you to know I am sending it to you and I hope you feel better soon.