Bad news first, this is gonna take way longer than you think or want to believe it could take and it's gonna keep popping up even when you think it's gone. Good news, you're admitting there's a problem, you're working towards a solution and you're considering other perspectives. Validation is key, look for local peer support groups, somewhere you can share and listen to others experiences, in person ideally. I've been through similar experience and I've been able to reframe it into working towards helping others through finding that validation and learning more about the topics. You don't have to do any of that but I'd advise at least therapy to help reframe the issue.

Tl;Dr You're not mediocre and you're not being dramatic, you're thoughts are justified but they are incorrect, it's far easier to focus on the negative than the positive.

I am highly educated (PhD in Engineering), have my own house (valued at $1M+), am fairly good looking (pull both ladies and men), have a decent enough resume with fancy names on it This is who you are, now you just have to believe it.

Ps. I'm not a professional, I just have a specific interest in the topic.

Pps. Feel free to DM if needs be.