Hello Rose, the first thing that comes to mind is some sort of microbial infection. You may have a subacute infection caused by leaky, herniated or twisted gut, injury to other area if the body, or from contaminated food or water.
Whether the infection is bacterial, fungal or parasitic microorganism, it can cause sudden onset symptoms that you describe, as waste from micro organisms is toxic, and microbial overgrowth and gut problems of any sort can result in mallabsorption of nutrition by diverting food sources.
Unfortunately, western medicines isn't really set up to detect, diagnose or treat this sort of illness. Even if you do testing, there isn't any guaranty that the sample tested will actually be contaminated tissue, stool, whatever, so that probably isn't your best route.
I'd start with an Infectious Disease Specialist I feel you have access to this sort of Doctor. If not, you're pretty much on your own.
If it were me, I'd start with a good quality vitamin and mineral supplement, as well as a psyllium colon cleanse and herbal parasite combination supplement series.
I'd also see a chiropractor and have them check for inguinal or other gut herniations. I'm not sure if they're allowed to diagnose, but they can likely tell you if you need to look further into treatment for hernia. I would also see an acupuncturist because they treat general health, and you may get some relief. The acupuncture also examines completely different than western medicine, so they may give you some hints as to where to look.
While I'd incestigate the microbial angle first, there is always the possibility of other endocrine disorder such as hypothyroidism or adrenal exhaustion. However, the sudden onset of symptoms and the fact that microbial treatment resolves a ton of systemic problems indicates this is your best approach, infection is a short term problem if treated, and may resolve many of your symptoms. If you get no relief from microbial treatment after having investigated fully, you can look at other issues.
But honestly, I suspect you'll get relief from my suggestions. Feel free to pm me if you like.
Good luck and I hope you're able to feel better.