Having been involved with someone for several years, who was later diagnosed with a personality disorder, I can relate to many of the difficulties you describe.
Perhaps it's easier to see now that it's behind me, but probably my biggest "takeaway" from the whole experience is the importance of staying in touch with oneself and our own feelings. And we need to respect those feelings too. All of that always takes some effort in even the best of conditions, but it's especially easy to lose sight of your own needs and boundaries, when you're constantly dealing with another person's needs & emotional chaos.
If nothing else, you can't find solutions to problems when you're just reacting, and unaware of how you really feel.
So be sure to take care of yourself, and that also includes not being too hard on yourself as well. Good luck!