I try to be very careful to which subjects I reply to as I don't want to further confuse the subject. I am a writer so wording is important to me. I carefully analyze all the words brought forth to make sense of what is being said first. For instance the word 'Demon'...
de·mon [dee-muhn] Show IPA
noun
1.
an evil spirit; devil or fiend.
2.
an evil passion or influence.
3.
a person considered extremely wicked, evil, or cruel.
4.
a person with great energy, drive, etc.: He's a demon for work.
5.
a person, especially a child, who is very mischievous: His younger son is a real little demon.
I thought it odd that they would refer to a 'demon' in definition 3 and 4 as a physical entity as opposed to a spiritual entity.
In my opinion:
Demons are a whole other level of energy. I don't personally believe they bother with us. A little stuck up if you will. It's kind of like being born into money. You know who Paris Hilton is but will you ever meet her...NO. Now I do believe in extraordinarily negative energy and I would compare them to being like the body guards of Paris Hilton. You will encounter negative energy (body guards) before you will ever IF ever meet a demon.
I think negative energy has attached to your boyfriend. Yes I would suggest like CC suggested to look into medical/science explanations and keep an open mind...but something is nagging me to say it's negative energy. Almost like a force to be reckoned with that can see he's vulnerable and so they 'play' with him because it's easy.
It takes a really strong individual to ward off mischievous energy/spirits. He picked it up somewhere...The thing is to find out where, stay positive, get to the bottom of it and let them/it know there's no 'Welcome' mat on his body.
Hope this helps. I really encourage looking up words...sometimes definitions alone explain everything.