As you have had this rash for so long, and your rash on your chest comes and goes, it very much sounds like you have an allergy of some sort.
Use non biological washing detergents and rinse your clothes well.
If you are using any sprays, soaps, shower gels, shampoos, you may have an allergic reaction to that.
Sometimes it is just trial and error to find what causes a problem.
Do you have any contact with plants where the pollen or other airborne pollutants are getting on to your neck?
Are you touching something that is an irritant and then touching your neck without first washing your hands?
You could also try an antihistamine that you can buy from the pharmacist, that won't cost much and worth having a go to see it if helps.
Hope you manage to sort out your rash problem. It may take a while if you are going to try and eliminate things.
Consider seeing a proper allergist, or maybe a dermatologist, and ask them to schedule you for a long appointment so that you'll have time to go over things. A good allergist will take an extremely thorough history to try to find out what causes it. In addition to soaps, certain fibers might be causing issues over delicate areas. Don't wash the area with soap unless it's really dirty, and try the hypoallergenic soaps.
Some people get urticaria (hives) from things like heat, cold, or even water. The chest and neck are pretty sensitive, so I think it's possible that you have some sort of trigger that's constantly present. A relative of mine gets mild urticaria from water. It's something to think about, at least.
Have you tried taking antihistimines? Did they help at all? Advice from Jemma and Anonymouse are right on. Also, you might try using a cup of white vinegar in your last rinse water when you wash your clothes. The vinegar will remove the soap/detergent.
Thank you all for your input by the way! It seems extremely overwhelming and hopeless after 4 years of trying to rule out what may be the cause if this is in fact hives. I've been using the same washing detergents, soaps, and shampoos since I can remember and the rash still happens to go away from time to time so I have certainly ruled those out. I currently don't have a job as of 2 weeks ago and it has been looking the best it's ever been since I've had them. Weirdly the only thing that has changed in my unemployment is that I'm less active. I was curious if maybe sweat was the cause so I went and played tennis for 3 hours till I was drenched and still the rashes have been barely visible for almost 4 days now. Very interesting situation for your relative Anonymouse88, I do sometimes take really hot showers. I'll keep that in mind. I will certainly try antihistimines on my rash areas and white vinegar in my rinse water.. thanks for the suggestions jemma and silver. I'm going to wait until my rashes decide to pop back out before I do though just in case one of these things irritate them for some reason and force an occurance. I appreciate all of your responses. You've officially all shown more care than my doctor.
If I had to guess, at this point I would honestly say it's either stress related or heat related. As soon as I'm able to go to an allergist or dermatologist I certainly will. I now have a few things to try in the future as well. Even if they don't work, the still provide a little hope and chance that they may. That is better than the feeling of having no hope. Thanks again.
I have an Aunt that is allergic to her own tears - and being allergic to ones own sweat is not unheard of. I knew a fella once who was "ordered" by his doctor not to sweat as it caused adverse reactions in him. A bit strange, but possible. As for the detergents, fabric softeners etc. you can become allergic overnite... I did. I can't use my Mom's products - they hurt my skin. If I touch Dawn my fingertips peel and I get cracks on them. Just a thought. My sister uses only Borax to wash her clothes as she's become allergic to all detergents... But hives can be caused by anxiety - in which case you might try a Kava tea or Chammomile tea to de-stress you. - So sorry your doctors let you down. They are "practicing" medicine...LOL They are only taught which meds to prescribe for whichever condition. they are not taught nutrition or herbal formulas. A chiropractor knows more about such things. Good health to you