Follow-Up:
I have had similar experiences, tho one stands out. It was the summer of 2004 and I was feeling alone most of the time while my friends cavorted with their real life girlfriends in the sun. I lay on my bed most nights reading fantasy books to lost souls of the darkness...when suddenly I start arcing like nothing ive seen in porn films or in 1st person...like my back is being tested to breaking point...I had energy shooting right thru the length of my spine. It wasnt a demon i know this, because ive been fucked by a demon and all that felt like was have my head carved up by a thousand knives :/ I've stopped dabbling with the occult since that was a nice point to leave it on.
Here is a link that might be useful: My Art Website