Wonderful to hear about medication helping you sleep! I agree with Smallwolf with the psychiatrist; I am sure that the reason you haven't heard back yet is just time. It would be a good idea to follow up and hopefully there's not a long waiting list.
Hm, thank you for sharing with us why you are scared. That makes sense. I too am proud that you decided to reach out and get some help- that's not easy! I think that these feelings are part of the pros and cons of a diagnosis and what that would mean to you if it was BPD. I'm not sure if it will be helpful, but try to remember you are M before you walk into their office and you are M when you walk out of their office.
A diagnosis can be really powerful, but all it is is a clinical name for a bunch of behaviours. Pretty much all of us will meet bits and pieces of various diagnoses but not necessarily fulfil the criteria for one. BPD, anxiety, depression, trauma - it can all be managed and worked through. You don't need to be fixed, because you're not broken.
I hope this helps a little! Best of luck with the counselling session today; hope it goes well.