I'm glad that you wrote in with this sleep question, because hopefully I am going to put your mind—and your spirit—at rest.
What you describe occurring in your sleep actually is a common event known as a confusional arousal. You state your experience was not a dream, and this is true! Confusional arousals are not dreams, but they are events that occur out of very deep sleep. As a rule they are terrifying, and it is common for us to feel an evil presence in the room, and to fear that we are about to be attacked.
During a confusional arousal, we partially awaken from deep sleep, usually due to a bed partner turning or rolling over, or to a noise outside our house or apartment (a car door closing, for example). Because sleep is deepest during the early part of the night (the first three hours), it is difficult for us to fully awaken during this part of the sleep cycle. And sometimes—our brains get stuck between waking and sleeping.
Scientists in sleep laboratories have demonstrated that during these arousals, part of the brain shows waking activity, while part of the brain remains deeply asleep. Confusional arousals also are related to sleep walking and sleep talking, which also occur out of non-dreaming sleep. In children, confusional arousals are called night terrors.
The half-awake, half-asleep state is confusing and disorienting. If the room is dark, we also can feel vulnerable because we are unable to orient ourselves, and soon we can begin to "see" (imagine) that there is an attacker in the room, standing over our bed, about to attack us. Or, like yourself, we may become convinced that there is an evil presence in the room.
To read more about confusional arousals, please visit Walking and Talking in the Sleep Disorders section. You will quickly recognize your symptoms in the accounts of others, which will relieve your concern that your symptoms may be unknown or unique to yourself.
Will you believe that this "evil presence" is afraid of the dark? It's true! Sleeping with a nightlight eliminates confusional arousals, because the light allows us to recognize that all is safe, and we simply roll over and return to sleep. Also, during a confusional arousal, your husband should simply try to assure you that there is no danger (turning on a light is the fastest way to bring an arousal to its conclusion), and to encourage you to return to sleep.
There is no deep psychological trauma or repressed subconscious event that causes confusional arousals. Instead, it is a simple physical event caused by difficulty awakening from deep sleep. The reason you have these events when your husband is not present is because you are sleeping with "one ear open." With your husband gone, you are more prone to arouse from sleep when you hear a noise or are startled.
Please read the section of the website that I have referred you to, and starting tonight, begin to sleep with a soft light on in your bedroom. If the arousals are not immediately eliminated, try increasing the amount of light in the bedroom. The light will solve your problems with the arousals, and it will make the evil presence vanish!