Nacho, Not to make light of your plight, but attacks by astral entities are very real. They do happen and even enlightened people have been known to fall from grace.
Somehow you attracted them or unwittingly let them in. They love to feed off people's energy (and more) and when doing energy work, it is necessary to take unusual measures as they may take notice.
First you have to clear your own body of them. It's often easier to have experienced consultants do the work for you. Then you have to learn various techniques of psychic self-defense. Better yet try to get a permanent energy shield.
Many people do this type of work from Tibetan monks to new agers. Everything in the universe is energy including thoughts. We all have a responsibility to cover our assets. 
For a couple of examples see
http://www.clairvision.org/CKB/CKBB/CKBB_000_218/Index.html
http://www.christaresources.com/default.asp?P=4
"The topic is both old and new. Old, because in all traditions and folklores of the earth, one finds references to spirits and non-physical beings which can interfere with human beings. Thus Ayurveda, the traditional medicine of India, is divided into eight sections, one of which is entirely devoted to the study of bhutas, or entities, their influence on health and sanity, and the ways one can get rid of them. This places bhuta-vidya, or 'science of entities', on the same level as surgery or gynaecology. If we look at traditional Chinese medicine, we find that in acupuncture, among the 361 points of the 14 main meridians, 17 have the word Kuei (disincarnate spirit) as part of their main or secondary name."
[This message has been edited by shr33m (edited September 20, 2003).]
