This post will probably be all over the place, as I'm not completely sure how I should organize it.
I've been experiencing a depressed mood swing for about four days now. I've been feeling bad about myself, I've been overly emotional (crying immediately after thinking one bad thought about myself), and I've been thinking a lot about self harm (though I have not acted on those thoughts). This is the first actual mood swing I've had in about 5 1/2 months, and the first my boyfriend is witnessing (we've been together for 5 months). 

When him and I met, I had just gotten out of an extremely toxic relationship a week or two prior. I dated a legit psychopath on and off for two months, during which he repeatedly discard me and then would take me back, I relapsed with self harm (now roughly 7 months clean), and I went to the hospital and was diagnosed with BPD. The relationship was terrible to say the least, and it destroyed me for awhile. The first couple months of this current relationship were a bit rough because of it. I absolutely should not have jumped into a relationship so soon after what I went through, but it just happened that way. My current boyfriend brought me out of that bad place almost immediately, and everything has been perfect between us thus far. This is the first real relationship I've had.

Now that I'm in one of my mood swings again, I figure now is a good time to educate him on what BPD is so that our relationship will work out and be healthy. I've always been very aware of my BPD and I truly believe I have it under control and managed. Meaning that when symptoms come up, I recognize what's going on and I don't do anything drastic like I would have in the past. 

I read several posts on the subreddit for past/present significant others of people with BPD seeking advice and whatnot, and now I'm kinda freaking out. They talk about people with BPD as though they're insane and severely unstable and just all around crazy. And while unfortunately that may be the case for some, I don't think my BPD is nearly as severe as the cases mentioned there. But now I'm paranoid that all of that's gonna happen with my relationship. 

Which finally brings me to my point. I am determined to make this relationship work. What steps should I take to make that a reality? Should I start seeing a psychiatrist? Couples therapy? What should I be doing differently? What's the best way to go about telling him about BPD? He knows that I suffer from mental illness, but he doesn't know the full extent of it.

TL;DR I have BPD. What is some advice on how to have a healthy relationship with my bf? 