It depends upon the cause really. Brandi et al 2006 showed that the stomach is frequently infected with over 600 micro-organisms being found. This is NOT normal but very common. Antibiotic resistance is making the situation far worse because even treatment with triple therapy for helicobacter does not destroy them.
There can be a bit of a chicken and egg situation. Stomach acid is needed to separate vit b12 and protein so that b12 can be absorbed. Lack of b12 can affect the nervous system which can cause low acid production due to changes to the nervous system in the stomach.
In the short term Betaine HCl caps might be helpful unless you do have a urease positive infection, in which case it would be wasted because it would be quickly neutralised.
I would recommend that you get some vitamin b12 as a start to help protect your nervous system. I would stick to about 1mg/day and not go above this because there can be negative effects above that. Maybe liposomal hydroxycobalamin or methylcobalamin types and not the cheap and much less effective cyanocobalamin.
Look up the supplements to help with methylation as this would be helpful, especially if your body is dealing with the high detox demands of Increased Digestive Permeability aka Leaky Gut. B12 is one of them and folate among others.
I would then do as I started with a sodium bicarb test to get an idea whether there is any stomach acid and a rough idea of how much.
If that shows little or none then I would do an acid test to test for possible urease positive bacteria activity. This largely depends on the urease activity of the bacteria as some are much stronger than others. Helicobacter Pylori is the strongest and there is a Staphylococcus bacteria, staph. captis urealiticum which is also quite strong others with lesser urease activity might not produce any noticeable effect. Neither of these is highly accurate but they cost virtually nothing to do and will give an indication of possible problems.
To do this you need some acid such as lemon juice or vinegar. Mix two glasses, one with the acid and some warm water and another with some sodium bicard to wash around your mouth afterwards to neutralise the acid in your mouth to protect your teeth.
Suck as much saliva into your mouth as you can. The urease enzyme produced by these bacteria use the urea in saliva to neutralise stomach acid by producing alkaline ammonia and can produce large amounts of damaging ammonia in order to stop stomach acid. Then take the acid into your mouth and mix it with the saliva. Then swallow it. Then start timing. It might only take about a minute to produce a burp/wind.
See how you get on with those two.
If there is any evidence of a urease bacteria then you will need to destroy them, which can be very difficult as I am attempting to do so myself. I have not yet found everything that I need but I am getting there slowly. I have other problems though and not just low stomach acid and at least 5 large infections causing very high permeability of my digestive system.
I have read a pile of research papers on connected subjects such as biofilms, efflux pumps, quorum sensing, cell membrane altering substances and essential oils both efflux pump inhibiting, antimicrobial and cell membrane altering. I found some useful info earlier about a pile of natural efflux pump inhibitors against recognised bacteria see "A review on Efflux Pump Inhibitors of Gram-Positive and Gram-Negative Bacteria from Plant Sources" Rakesh Kumar et al 2016. These will all help to defeat the bacteria. Curcumin (from Turmeric), Green Tea (EGCG) and Capsaicin are a few things which can affect bacteria cell membranes and also for Green Tea, provide efflux pump inhibiting effects.
Making sure that you get more than sufficient Boron might be helpful. This can be helpful with joint pain and also hormones. I would recommend at least 12mg/day, 18mg would be better. A cheap source is Borax but I forget the amount of boron in borax. You can find that on the web.
BTW the mucous and possible runny nose when eating are caused by high histamine levels which is triggered by the immune reaction to incorrectly digested large food molecules due to Increase Digestive Permeability. This is a mechanism the bacteria use to procure large amounts of urea in the salive/mucous. They set up an effective feedback mechanism which benefits them and they use the normal human bodies responses against itself.
BTW2: Constipation is caused by a lack of acetylcholine which stimulates the bowel. This is very common and caused by the liver using up all available choline for other purposes due to the high demands placed upon it to detox waste products incorrectly absorbed into the bloodstream. Taking a little lecithin can be helpful as phosphatidylcholine is required for cell membranes and the nervous system.
BTW3: You did not answer my question: Why do you need to spend so much time in bed? Joint pain? Tiredness/exhaustion? Just feeling like crap? All of them?
BTW4: It might be worth seeing my post in the eBooks forum for free access to full research papers if you want to read any of the mentioned papers which are closed access, the Brandi one might be. ;o)