Any ideas on what these are?????

I have been getting these "episodes" of jerking, twitching muscles for about 1 1/2 years now.  When these episodes come on, I get very sick to my stomach and throw up (violently), get dirrehea (severe), my heart will palputate, breating becomes shallow, my speech will start slurring, my vision will get dark and tunneled and my hearing is off.  It will start with quick jerks in my arms, then my head will jerk to one side, my jaws tighten up and will often clench.  My walking is off and I sometimes feel off balance and gait is not normal.  I do not lose conciousness and am fully aware of what is going on although, I am not fully funtioning mentally.  I will feel all the muscles in my body tighten up and then have sporadic jerks or tremors in my arms and legs.  This goes on for about 1-2 hours with periods of muscle release and then retightening of all muscles.  I will usually get a sense of panic during them because I am so scared that they are going to kill me or that something is seriously wrong with me.  After the episodes are over, I am exhausted and usually fall asleep.  For the next day or two, I feel little "aftershocks" where I might get a few jerks in my arms with a feeling of anxiety that I am going to have another attack.  I don't want to go anywhere for fear that I will have one while I am out in public.  They usually happen a day before of the first few days of my period but not always.  They usually happen at night (I have had only one during the day).  I had an MRI, which came back normal and had two 20 minute EEG's which also came back normal.  I am currently not taking any medications at all.  Can anyone help me figure out what these are and how I can stop them....?????  Please help, they are very distressful.