I've never known a three year old who wasn't picky about what they ate, and often the parents worry that they aren't even eating enough to sustain life...but they are and this phase passes. To be losing weight is of concern, so work closely with your pediatrician on this. It sounds like she can communicate very well with you, so ask her where it hurts her to chew, gather all the clues you can so you can tell her doctor. She may also have a sensory disorder where she prefers soft foods over any other. If she stops losing weight and is found to be healthy, the less a deal you make of it....the better. Don't make mealtime a stressful time for her and cause her to be anxious. Best wishes and good luck!
Welcome to the anxiety forum!
With a three year old child, you're going to see all sorts of stages with her eating. You did the right thing by taking her to the doctor, which is what you need to continue to do. If you feel some of this is behavioral, you need to set limits and be firm at mealtime. In that case, the answer isn't giving her whatever she "likes', you must remain consistent so that your daughter knows YOU call the shots.
The very last thing I would worry about at this point is that this is somehow anxiety related. Most eating issues with children this age are related to behavioral issues and wanting to eat only what they like. It could be food allergies as well, which is why you need to keep the lines of communication open with her pediatrician. However, food allergies and intolerances would typically present with a lot of other symptoms, diarrhea, nausea, gas, bloating, etc., which you don't mention.
Lastly, and possibly the most obvious next step here is take your daughter to the dentist. She says she "can't chew" which may indicate something is hurting in her mouth. The other clue that this may be an dentition issue is the fact that she's agreeable to eating soft foods. This could be an impacted adult tooth trying to come in early, a premature loose tooth, etc. THAT would be the next logical assessment and then go from there.
Best of luck....let us know how she's doing...hope you figure it out!