Most likely you have created a sourdough starter, which is a microbial colony containing yeast (make it rise), and Lactobacterii (produce lactic acid, make it sour), and other microbes that give it a unique flavor.
But why is the cooked dough soft and rubbery and not bread like? Lactobacterii digest gluten, and have has had 6 weeks to turn all of the wheat gluten into food. Which is why the dough is now soup like (that and the yeast digesting all of the carbs). And gluten as a protein, is what gives your bread structure, no gluten = no structure. The rubbery bit probably comes from undigested bits of gluten and other carbohydrates.
What can I do with it? Try adding some flour/water and see if it is indeed alive (I've had sourdough come back after being forgotten for 7 months in a refrigerator.. I've also had sourdough that died after being forgotten for 3 weeks). If it is alive, and you like how the bread it makes tastes. Congratulations! You have created a sourdough starter on accident.
Note the more traditional way to create a sourdough starter is to use a mix of equal parts whole wheat flour and water, and then wait somewhere between 2 days and 3 weeks with the starter at room temperature, with fingers crossed that it will start bubbling, instead of growing mold (though after 2 weeks, it's better to repeat the attempt... don't want a slow growing yeast).
There was some excessive concern about food safety in a heavily downvoted answer, but for future refence this is how you tell if food is bad:
Smell, does it smell bad? If so throw it away. The human nose is remarkably good at detecting a wide range of toxic substances.
Appearance, does it have mold (green, or black specks) growing on/in it? If so, throw it out.
Does it have a live culture (such as being a sourdough starter/ wet yeast). As long as the sourdough starter is 'alive' the yeast/lactic bacteria will prevent other microbes from colonizing it. It should be fine. (this is why raw milk goes sour and is still edible for a time... while pasteurized milk goes rancid and is inedible).
The bacteria that you have to worry about with bread:
E. Coli bacterium, A bacterial infection is not a concern as it dies at 160 F. A specific variant can produce E. Coli Shiga... produces Shiga toxin which is inactivated at 212 F after 5 minutes which might be a concern as most bread is considered 'done' when the middle reaches somewhere between 190F and 210. But I wouldn't be to concerned over it as E. Coli produces an unpleasant sulfurous odor, which is noticeable
Salmonella dies between 145 and 160 F. If you cooked the bread, not a problem.
Everything else, highly unlikely.
- Clostridium botulinum is an anaerobic bacterium, unless your bread dough was in a low oxygen environment (such as a sealed can) it's fine.
Finally as with everything in life:
- Trust your common sense. If there is something that looks off about the food. Throw it. Its better to be safe then sorry*
*That being said, we wouldn't have bread, cheese, butter, wine, beer, lutefisk, vegemite, mead, soy sauce, fish sauce, ketchup, raisins, beef jerky, cooked meat, etc.. If someone hadn't ignored their instincts that said "don't try anything that looks weird"
