Major Depressive Disorder (MDD) and depression in general is a thing I deal with. Something it's important to remember about MDD is that the disorder is characterized by the episodes. So, once you've had a major depressive episode you will be diagnosed with MDD. You may not have another episode for quite awhile, if ever. There are so many factors that are at play, and science is still trying to understand it.
Your depression diagnosis can shift over time, depending on how the depression behaves.
It's also difficult when it's co-morbid with PTSD, because depression can be a symptom there - or, the PTSD can trigger a major depressive episode. Most people don't worry too much about drawing the line for themselves, which is which. I was diagnosed with depression before PTSD, and I think because of that have an awareness of where my depression is coming from, generally - whether it's part of my PTSD, or it's own beast.
Borderline has never been described to me as anything other than a lifetime disorder, but one that is well-managed (nearly to the point of remission) with DBT. That takes a concentrated period of work in order to really lay the foundation, and then a ton of just straight-up skills practice. But, it's something you can get under your control, if you choose to and have access to the proper resources.
I'm not certain, but I might guess that your anxiety disorder is not a stand-alone, but is really absorbed into either your PTSD profile or your depression profile...Or, it's possible that your depression is in your PTSD profile, as well. Disordered eating can be understood as a symptom umbrella-ed underneath depression, anxiety, or PTSD.
I might suggest that it could help you to re-evaluate your understanding of these diagnoses, and look for ways to understand how they are nested in each other, and where the most prominent issues are. For example, PTSD has prescribed therapies, protocols that are known to work. If you could engage in trauma processing in a pretty diligent way, and be knocking the PTSD back to a much less activated state, you may find that your depression and anxiety issues recede enough to be occasional and manageable/negligible. BPD all by itself is generally going to make things seem more impossible, or more crisis-oriented, and more desperate than they may be. If what's happening for you right now is, you're unable to get a good hold over your emotional life, and your relationships are severely suffering and you are feeling wrung out with it all the time - you would probably choose to go all-in on a formal DBT course, and plan to do 2 cycles. You'll end up getting a lot of relief from the emotional tidal waves, and those are skills that are going to help you in spades when it comes to PTSD symptom management.
Anxiety itself can be 'parked' with medication for a bit, just to give yourself a leg up on working the other stuff; it's the same reason (I believe) that PTSD people are so often given anti-depressants. It's just to lift some of the weight of it all, the impossibility of things, while doing focused trauma work.
Of the things you've mentioned, what would you say is your personal biggest daily struggle (symptom-wise),
@Punky143? And, what would you say is affecting your interactions with the world (work, family, etc) the most? (they might not be the same thing).