What Causes Severe Insomnia?

Hi my name is joah.I hope you can help me. For years now I ve been having problems sleeping. I find myself drifting off until a HUGE convulsion propels me upwards, these can sometimes be so powerful my body leaves the bed entirely. (in not exaggerating) sometimes i have discomfort in my chest beforehand, like a trapped wind feeling. My doctor has always put this down to ibs or acid reflux but it just doesn t feel that it is after looking through the symptoms of each. I ve developed anxiety problems now as these huge convulsion/spasm/palpitations leave me in a state of pure shock and panic. Please please help. Im at my wits end.