This may take some time to explain just like it will take time for you to use it. Because doctors have little time and GPs have little information. "take a pill" is their usual approach. For many it works.
We are born with very little knowledge which is why the first 11 months are critical. This is based on a thing called attachment theory. The information you store in your memory gives you your personality and how you look at life. This is also the beginning of core beliefs. What are core beliefs? Core beliefs are blocks of information in your memory that you call upon to make every decision you make. Every decision! Almost all of which you do subconsciously at the speed of light. The next 6 years of your life you build on what you learned in the first 11 months. This period you build more core beliefs and reinforce the ones you already have. And here is the bad part. If they are wrong for some reason you will still reinforce them because they are telling you they are right because of some misconception or reinforcement from outside sources.
An example is like this. If a child is told they are stupid by someone unimportant they can ignore it. But if some one they are attached too during this learning curve such as a parent tells them the same or agrees with the unimportant person then this forming core belief gets reinforced and even if it is wrong, it becomes right in your mind.
Okay now you know what core beliefs are and how they work. Do you have someone you trust to tell you the truth even if it hurts? How you change core beliefs to the better is by challenging them and correcting the ones that are not true. But, and I think by what you said in your post you can accept the ones that are right even if they are unpleasant. Recognizing them and accepting them gives you a real, not perceived base to work on. You will slip back into the old routine periodically because core beliefs are strong and it is easier to accept them than fight them. They are harder to challenge when you are tired and panic does cause fatigue.
This is why I asked if your girl friend would carry you and why I ask now if she will help you challenge the core beliefs. Oh and you never stop building on core beliefs and adding new ones. The new ones are what you want to use to control your life, not any that are false. Don't presume, that they are all false. Some must be or you would not have reverted back to where you are.
This change in life you are going through is the trigger that opened the flood gates and allowed your memory to scare the crap out of you and bring back the panic.
There is no short cut. You will have to use every coping skill you have and any you can learn here to keep you in a state where you can successfully challenge what is happening to you and straighten it out.
I'll not say, you did it before, you can do it again because this time the trigger may be different, but the CBT process is the same no matter what is causing the problem.
This is doable. I'm living proof of it.
Here to help anyway I can. All this information is my perception based on that supplied by my Ex Therapist and corrected by her. It is only information to be checked and/or used any way you think you can.