My dentist ground my first two front teeth and my whole bitefeel changed. could only my back teeth touching lead to tmj? does this affect digestion and lead to stomach problems?

Hard to say: It is hard to say what is going on with your TMJ problem, but a change in your bite can cause your jaw to be more painful. Why were your front teeth adjusted? What kind of issue did you have before this? See a dentist that treats TMJ for an evaluation. Tmj is not related to digestion problems, this is a different problem.

Talk about joints: Tmj is multi factorial, meaning many causes. Just having only posterior teeth touch usually doesn't lead to TMJ unless you add something like clenching or grinding. Your other medical issues can be leading to stress which can affect your joint.Discuss with your dentist about your issues.

Tmj: There are people who can get along with only their back teeth touching and have no problems. The "normal" bite would have anterior contacts also with the cuspids (canine teeth) guiding your bite. If thats how things felt before, you should talk to your dentist about adjusting it back. That alone would not typically affect digestion. Your back teeth still grind the food up fine.

Balanced bite: A balanced occlusion (bite) is important to preventing other health problems.

Complex problem: TMJ and bite problem related. I'd recommend a TMJ specialist to sort things out.Any dentist can be a TMJ expert with the proper training and experience. Most commonly, oral surgeons, prosthodontists, and orofacial pain specialists. Ask your MD, your dentist and your dental society for referrals.