Stuck in dreamland

Have you experienced a time whereby, when you were sleeping and you want to wake up, but you just can't. You struggle to open your eyes.. like you just CAN'T open them and in your preconcious state, you keep telling yourself to open them. Then, you can imagine the external view, your surroundings, trying to make your body to wake yourself up, but you just can't?

Ever feel as if you just can't get out of your unconcious/preconcious state? Just stuck there, unable to get up or move yourself at times... struggling.. As though, someone was pushing your body down or someone sitting on you. Your body just felt as though it was pinned on the bed/couch you were sleeping on.

Terrible feeling, rite? After long hours of sleeping, you feel even more tired than before.

Anyone can explain all these to me??? It seems kinda scary. I feel that quite often now. Is it because my body is extremely tireed & crying out for rest? I have been sleeping earlier than before (I think!). Any other explanations?

Felt as if I was in coma... The difference is, in coma, you can't get up for few months or years.
Felt like sleep apnea, but in that state, you are gasping for air & unable to breath at the middle of your sleep.

So, what is it? Does it often happen to you?