I used to have the same problem and still do sometimes. I never used to be able to make new friends and hated when people worried about me (still bothers me greatly). It all takes time. If you work at it hard enough, you'll get to know yourself and wat the disorder does to you and start to control it. You'll be able to catch yourself when you're rambling and talking too loud. When you get to this point you can then turn the conversation back on the person and give them a chance to speak. For me this has led to very in depth meaningful conversations with complete stangers.
I feel your pain, Secretum, i really do. For me it too 4 years of college to really open up. It took getting up and speaking in front of large groups of people, forcing myself to meet new people.
One method is to "screw" yourself. Walk up to someone, attempt to shake their hand, or whatever greeting you use, and introduce yourself. If they do as much as introduce themselves, you just "screwed" yourself into talking to them. Simple as that.
Good luck. I'd be glad to answer any questions you have.