If the hospital has run only the usual conventional medical tests on you, it's unlikely that they would have measured the levels of the metals. Unfortunately, the conventional medical tests were not selected with ME/CFS in mind. I don't know in which country you live or what testing is available to you. In my opinion, the best test panel to run for CFS is the methylation pathways panel that is offered by the Health Diagnostics and Research Institute in New Jersey, USA, and the European Laboratory of Nutrients in the Netherlands. This test panel looks for what I believe is the core issue in the biochemistry of ME/CFS, which is a partial block in the methylation cycle, coupled with glutathione depletion and draining of the folate metabolites from the cells. If a person has this core issue, then in my opinion they have ME/CFS, and there is a treatment for it that is non-prescription and not very expensive. This treatment has helped most of those who have tried it, and a small number have reported complete recovery. However, most have not recovered completely and the challenge is to find out what else needs to be done for them. This needs to be done individually, because not everyone with ME/CFS has all the same additional issues.
You mentioned fainting in the shower. This is very common in CFS. It is caused by the fact that the total amount of blood in the person's body is less than normal. When they take a shower, more of the blood is sent to the skin in order to regulate the body's core temperature, especially if it's a warm shower. This does not leave enough blood to go to the brain, and that's what causes the fainting.
The low total blood volume results from a condition called diabetes insipidus. This is not the same as the more common diabetes mellitus, which involves blood sugar and insulin. Rather, it is caused by insufficient production of a hormone called the antidiuretic hormone by the hypothalamus/pituitary in the head. This has been measured and found to be low in people with ME/CFS. In my hypothesis, called the Glutathione Depletion--Methylation Cycle Block hypothesis for ME/CFS, it is caused by depletion of glutathione in the hypothalamus/pituitary. In this hypothesis, there is also a genetic component to ME/CFS. The fact that your mother appears to have Asperger's syndrome would be consistent with your having inherited a genetic predisposition from her. There are many cases of ME/CFS and disorders on the autism spectrum occurring in the same family.
If you would like to read more about this hypothesis and the treatment based on it, this information can be found at www.cfsresearch.org