Hair loss

hello, ive been looking around for info on this 4 a few days… I created a character, was pretty satisfied… thought id try to tackle particle hair again, ive experimented with it in the past… well I got the hair really good…the way I liked it… then noticed the face was a little fat… edited the mesh… or something like that… by this time I had three particle systems, well…hopefully you know what happened… I lost my particle systems… or they became quite broken… no big deal right? just delete them and start over… but the mesh is broken somehow… even a new particle sytem comes in broken, children wont render, hairs don’t show up… hair is disconnected from the mesh…also the density that should be limited by the vertex groups no longer function. it happens a lot… I now seem to know that one should never ever edit their mesh after adding hair. There should be an add on that screams this at you… before you consider adding hair to a model… or am I missing something… how to reset a mesh as though it were new… and can receive particle systems normally? Maybe someone can tell me if there is a way to salvage many days of work on the mesh… or do I just need to wisen up… and never ever edit and combine meshes and particle sytems… because it changes the nature of the mesh somehow… or the nature of electricity…and binary numbers… actually knowing what is breaking, and how or why not it cant be fixed would be enlightening… a button that says start over on your mesh…would be great…start from scratch… no penalties. promise would be nice.^^haha

ok, I did find one thing out, there is a button next to the slot for your vertex groups in the particles settings… the buttons tool tips, says negate the effect of the vertex group… its a little unhelpful because it doesn’t look any different in the toggled on or off state… now im getting hair from the vertex group that I had chosen… it would be nice if blender didn’t adjust your settings secretly and needlessly to negate your work…