Can you jus get genital herpes from within you from being run down etc or do you have to be infected by som?

Genital herpes is caused by the Herpes Simplex virus.
You have to catch it from somebody who is already infected. The bad news if you have it is that it is incurable. the symptoms can be controlled and the virus then retreats into the body where it sits at a nerve junction.
When you get run down the virus re-asserts itself and causes the symptoms.
Once you have the virus you will always be infectious.
Cold sores are the same virus and can cause genital herpes through oral sex.

yes, need to be infected. in contact. possible even from sharing clothing.

*not saying that generally people share underwear*
genital herpes can only come from sexual intercourse
Have to be exposed and infected by genital herpes or have contact with a person infected by it in your genital area
herpes is a communicable disease... it doesn't just appear. The problem is it can come from a multitude of sources and I suggest asking a doctor how it can be transmitted. That should give you some clues as to how someone can contract it.
You have to come in direct contact with the virus itself- either by your skin touching an affected person's skin or by coming in contact with the virus that was left behind on some inanimate object by someone who currently had an outbreak (usually within an hour or so).