I haven't posted to you much but can really feel your pain in your posts. I agree with souther gal. I had a friend in college that has borderline personality disorder. Your posts could be her so often.
There are self help things you can do to help yourself.
1. Play Music
Play music that creates an emotion that is the opposite of the one you are struggling with. For example, if you are feeling very sad, play happy, upbeat music. If you are feeling anxious, play slow, relaxing music.
2. Do Something
Engage in a highly engaging activity. Television or computer activities do not count here -- these are too passive. Instead, take a walk, dance, clean your house, or do some other activity that gets you engaged and distracts you from your current emotions.
3. Call Someone
Reaching out to others can really help when you are struggling with strong emotions. Call a supportive friend or family member. If you don’t have someone in mind that is supportive, call a helpline (for example, in the U.S. you can call the National Suicide Hotline at 1-800-273-TALK).
4. Pray
Are you a religious or spiritual person? If you are (or even if you’re not but have considered trying), praying can be tremendously helpful in times of extreme stress.
5. Ride It Out
The peak of most strong emotional reactions (and the urges to engage in harmful activities, like self-harming or drinking, that can go along with these reactions) last for a few minutes and then begin to subside. Grab an egg timer from the kitchen, and set it for 10 minutes. Wait the 10 minutes, and practice riding out the emotion.
6. Be Mindful
Practice mindfulness of your emotion. Notice the emotion you are having, and let yourself experience it as a wave, without trying to block it, suppress it, or hold on to it. Try to accept the emotion for what it is.
7. Breathe Deeply
Sit or lie somewhere quiet and bring your attention to your breathing. Breathe evenly, slowly, and deeply. Watch your stomach rise and fall with each breath.
8. Take a Warm Bath or Shower
Try to lose yourself in the sensations of the warm water, the smell of the soap, etc. Allow the sensations to distract you from the situation you are upset about.
9. Ground Yourself
When emotions seem to be taking you out of the current moment (e.g., you are starting to feel “zoned out” or can’t see anything else going on at the moment), do something to ground yourself. Grab an ice cube and hold it in your hand for a few moments, snap a rubber band against your wrist, “snap yourself back” into the moment.
10. Help Someone Else
Do something nice for someone else. It doesn't have to be something big; you can walk to the nearest store, buy a pack of gum, and give the cashier a smile and say "have a great day." It may sound silly, but small gestures like this can really reduce emotional pain.
The above was from an article on the Internet. There is a lot of really good articles out there about this. It's very real and not easy or certainly not a choice. The pain folks that have this is intense and heartbreaking. Not a desire for attention or manipulation, although those can be bi-products.
I'm sure you don't wish to burden others but you do know invested so many are in you on this site. They care and worry. It's so hard to watch someone in such pain an be completely helpless in easing or fixing it. Support can sometimes become enabling when the recipient can't or won't do what's necessary to help themselves.
It is up to you. While BPD, if you do have it, is a serious mental issue it is treatable and can improve. There are folks here that struggle with it and do very well. They have sought help, though.
Even if you don't have this reading up on it can help you see you are not alone with the struggles you experience. Other's have walked that dark lonely path and are walking it now. They have been able to see a glimmer of light, though and reach for it. I hope you can too. For your sake. For your SO's sake.