Throw away so my boyfriend doesn't see.

I've long suspected I have BPD. I've been diagnosed with depression, a variety of anxiety disorders, etc but it always seemed like that wasn't exactly it. I'm not trying to self diagnose, but everything I've read leads me to believe this might be me. I've found coping mechanisms that BPD people use (like DBT) to be fairly effective as well. Like many others, my life has been littered with unhealthy relationships, impulsiveness, terrible mood swings and burnt bridges. I feel like I can trace every bad event in my life to a random mood swing or acting on an impulse. Lately, I've been getting better about recognizing my moods and impulses, and letting myself feel my emotions without acting on them. There have been some successes and some failures.

I'm an extremely private person and I've told almost no one in my life about my struggles with my mental health. In addition to suspected BPD, I struggle with depression and maybe a degree of seasonal affective disorder. I live in a northern climate so the lack of sunlight and warmth this time of year always makes me feel extremely low. In the past, I've dealt with it by either basically "hibernating" for several months or by escaping south. I realize none of this is the healthiest, but for a few years it was the only way I knew how to cope. 

Now, I'm a full-time college student so I can't run away. I live with people and have a boyfriend of a year so I can't "hibernate" without people noticing. It's completely thrown me in a tail-spin the last month or so. I've been really depressed, isolating myself a lot, going through bursts of intense insecurity or sadness or hopelessness.. and it's been exacerbating the BPD traits A LOT. I'll go from being head over heels in love with my boyfriend to absolutely despising him to feeling insecure about our relationship to feeling completely despondent in a matter of hours. I always get these urges to leave at night when I stay over or to break up with him (before he breaks up with me, of course). I feel restless and unstable. For the most part I feel like I hide it fairly well, but I still slip up and act on these emotions sometimes. I feel insane. It's exhausting to live through all these emotions. I feel like I live in my head. 

It's been really hard to explain to my boyfriend. In fact, I haven't at all, I just keep trying to hide it. But I know it must be really confusing to have a girlfriend who seems fine but then randomly gets sad or angry or irritated or indifferent and leaves or won't text back. My depression also makes me really unmotivated and disinterested in anything I usually find fun. The combination of the two must be awful to deal with. The worst part is knowing what's happening and feeling helpless to stop it. 

I feel like most people would advise me to just tell him but I don't know what to say. I don't think I've ever sat a person down and told them about any of this. I deal with it completely on my own and it feels lonely and horrible but I'm terrified of telling him or anyone else. I love him but sometimes I think being in a relationship makes all of my symptoms worse. I feel like eventually he will get fed up with this behavior and leave, and I constantly struggle with the urge to just end it. 

I guess I'm just wondering how other people deal with BPD and relationships. It feels impossible to have both sometimes.