I completely understand and have the same problem. For me, I had to exam the following inside myself:
1) What control to I have? The answer is none, the ONLY thing in life you can control is yourself... period. You can not control they're action, comments, criticisms, expectations of you (how you succeeded or failed), and just the simple day to day way they talk to you and make you feel (in some families it's very supportive, in other's it's always tearing down, and other's it's somewhere in between).
2) Since you can't control them, you have to be honest with yourself and ask how much of them can I take and live a very happy, successful, satisfying life? Your first priority is YOU!!!!! You are of no help or comfort to your family (or anybody else), if you're wreck. So.... that leaves you with the following 4 options which depend totally on the depth of discomfort, meanness, care they really have for you, etc... essentially you have to gauge their intentions based on everything you know, have gone through, and gut feeling about them for the future.
1) In a phone call, be 100% honest. Start the conversation by saying "I'm having a real problem and need to know if you're willing to calmly discuss it with me, even though it may be very upsetting to you." If they are willing to talk, be completely honest, tell them you can hardly bare to be with them because it's so stressful, and above all tell them EXACTLY why it's so stressful.... pull no punches, because at this point there's no going back to the way it was... it'll end however it ends.
2) Depending on you, do the exactly same thing as above, except in person. This is tough (generally better in the long run), but not for everyone... you'll have to gauge for youself.
3) Tell them you're having some problems and was wondering if they'd be will to help you by coming to a therapist/counselor with you. In this case you'll have to decide on whether or not to tell them what's it's really about... in other words, you may need to sort of white-lie, or maybe you tell them straight out what it's about.
4) The final option is pretty simple. If none of the above seem viable for your situation and family... just don't talk to them or see them. Depending on your past situation with your family, and your personality that may mean calling them, telling them you want nothing to do with anymore, or maybe it's gentler like making up excuses that your busy, etc.
Anyway, in real life I believe those are all the options, and the correct options depending on the persons ENTIRE, life long experience with their family and they're own personality and ability to face things head on or not.