First, welcome, and sorry to hear you aren’t feeling well physically and mentally.
Second, I would stick to plain whole foods for a while and keep a journal of what you eat and any symptoms that may be happening. Then, take that journal to your regular doctor and review if there is any correlation. If they suspect an allergy, request a prescription for two EpiPens and a referral to a certified allergist for further testing. The most common foods that cause allergic reactions are peanuts, tree nuts, soy, wheat, milk, egg, seafood (fish, shellfish, crustaceans, molluscs), mustard, sesame, and sulphites. However, any food (or medication) can cause allergic reactions. Viruses can cause similar symptoms as well.
Search for the FARE Allergy Action Plan for a list of symptoms associated with food allergies: hives, itchiness, swelling, breathing difficulties, drop in blood pressure, heart failure, sense of impending doom, and others.
Call an ambulance immediately if you experience any shortness of breath, difficulty breathing, faintness, or pale/blue skin.
I hope you can find the cause of what ails you. I would definitely make an appointment with your doctor to discuss your concerns sooner than later, and come up with a plan to figure it out. In the meantime, this is a good place to ask questions.