You can't solve a thinking problem by thinking. Digging up things from the past and processing them is really hard to do alone. It doesn't have to be a therapist but there has to be a high level of trust. If the therapist can't do something as simple as get an appointment right how can you have any confidence in them helping you with what you are going through. There are good ones out there and like dating you may have to go through a few before you find someone that works for you.

Do you have anyone, friends/family that you trust to talk to? The nice thing about therapy is they are bound to keep your secrets and you can tell them to never bring something up again.

I'm not sure what type of help you are looking for. There are DBT "Dialectical behavior therapy" workbooks and tips out there. Not sure if you know what DBT is, but the short version is learning skills on how to deal with upsetting feelings. Like learning how to tolerate distress, how to gain some emotional regulation and a few other things. The nice thing about DBT is that they are skills you can learn and apply.