What Causes Jerking Of The Body And Dizziness?

well I was wondering if it is not normal for your body to have jerking spells I can be just sitting and all of a sudden my whole body would feel like someone shook me all of a sudden my head would do that to like just jerking spell .I do not like water I may drink it about twice about 16 ounces total could this be from dehydration and I have also a little lightheaded or dizzy when I am just standing or when I lean over to my left side I haven't slept on my left side going on eight years can u help me or is there anything I can take beside anivert which doe's not help what so ever and my right leg from knee to next to thigh stay swelled with fluid the one I HAD MERCER IN . MY DOCTOR SAY IT MOST likely from the mercer it may have affected the limp nodes I have had mri and Doppler test and scan and it shows only fluid from like I previous explained above the knee up to thigh.they have ruled out blockages. llz hep me