I had very bad myoclonic jerks when falling asleep due to vitamin B12 deficiency (B12 is essential to protect the myelin sheath around the nerves). Those jerks went away when I corrected my deficiency. Wikipedia has an indepth article about Myoclonus. Here is an excerpt...
"Myoclonus is a brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. These myoclonic twitches, jerks, or seizures are usually caused by sudden muscle contractions (positive myoclonus) or brief lapses of contraction (negative myoclonus). The most common circumstance under which they occur is while falling asleep (hypnic jerk).
Myoclonic jerks occur in healthy persons and are experienced occasionally by everyone. However, when they appear with more persistence and become more widespread they can be a sign of various neurological disorders."
Your symptoms may just be related to stress and anxiety. You can try magnesium supplements to see if this helps. But if symptoms do persist I would recommend seeing a neurologist to rule out anything more serious.
Hello~I hope you are doing better, if not, I may have some helpful suggestions for you.
First, I highly suggest seeing a chiropractor, you could very well have some misplaced vertebrae in your lower back, this would certainly cause the twitching and cramping.
You probably also are low in Magnesium and calcium, this two minerals, along with a good, high potency multi-mineral supplement are good for helping with the spasms.
Along with the mineral complex, I would also add a good, high potency B complex, these are the "nerve" vitamins and can be very beneficial in helping the discomfort you are having.
I hope you start to feel better soon. God bless you.