I have had sleep paralysis, often accompanied by night terrors (typically, waking up screaming/yelling in the strangest tones, throwing my limbs about), since I was young as well. I tried quite a few medications to stop this - generally some tranquilizer/sleep medication. The success of the meds varied, but some almost completely stopped these occurrences. I never stayed on the medications for too long though because I often felt groggy in the mornings.
The sleep paralysis and night terrors got to the point where I would sometimes have them up to ten times a night. These were often accompanied by hypnagogic/hypnopompic hallucinations. I was treated for a sleep disorder resulting in poor quality of sleep for many years. None of them were especially helpful, and I grew more and more tired over the years. I eventually got to the point where I may doze off while reading or something and almost immediately experience sleep paralysis, accompanied by a night terror.
Eventually, I was referred to a sleep specialist at a sleep clinic. After seeing the sleep specialist for nine months, the final diagnosis was idiopathic hypersomnia. All of the symptoms I was experiencing are associated with hypersomnia, especially the excessive daytime sleepiness - which was now my biggest problem.
I am now treated with stimulants to get me through the day. I am not confident in my diagnosis, but it's all I have to go on for now. I still have sleep paralysis and night terrors often, scaring everyone in the house (especially my dog or girlfriend, if they are in my room). I'm still tired all the time, and barely getting by with the help of prescribed stimulant drugs. . I'm worried I may fall asleep in class in university and have a night terror, which would likely be an unpleasant experience.
Anyway, sorry for the long post - hopefully you find some of this relevant. My advice though would be to see a doctor. Tell him every detail you can remember regarding the occurrences. It may be helpful to keep a sleep journal as well. You can log how you feel before bed (stressed, overtired, irritable, etc.) and other relevant information (where you slept, if you were alone, had consumed alcohol, were very hungry, had something on your mind, etc.). Make note of anything relevant after experiencing a sleep paralysis occurrence (details of any hallucinations, if you had been disturbed in your sleep, etc.). You may notice patterns of certain things which increase the probability of an occurrence. If possible, it is usually helpful to have someone wake you if you are noticeably experiencing unpleasant sleep paralysis/hallucinations. If you often experience these occurrences at the same time each night, try and have someone wake you before they happen.
Sleep paralysis can be caused by increased stress, excessive tiredness, alcohol consumption, anxiety, and it may also be a symptom of another sleeping disorder. There is also evidence to link hypoglycemia to hypnagogic hallucinations. In my experience, alcohol, stress, and excessive tiredness all worsened the occurrences of sleep paralysis and hallucinations. Though not the cause, they did increase the frequency of incidents. A doctor would be able to help you identify possible causes and decide on a treatment plan. Depending on the severity of your problem, he/she may also prescribe a medication (often a benzodiazepine). You may also get a referral to another doctor, such as a sleep specialist, if you condition is serious enough.
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