A. You should definitely see a doctor. I recommend that you see an Internal Medicine doctor or a Family Practice Physician.
B. It's not ALS. I've never heard of ALS starting like this.
I suppose it's possible for ALS to start anywhere. But I have two thoughts about this.
- First, you said you could straighten up if you put your mind to it. But ALS doesn't come and go whether you think about it or not. You see, ALS isn't really a muscle problem, it's a brain problem. In ALS, a motor nerve in the brain is destroyed, so it can't send a signal to its corresponding muscle. Once the nerve is destroyed, it can't rebuild, and that muscle will never again receive the signal needed to make in contract.
- Second, ALS is a rare disease. I typically starts in the hand or foot and works its way up (or down) the body. A few people get bulbar onset, where the tongue is the first victim, but this is even more rare. "Trunk onset" would be incredibly more rare than that.
Finally, it makes no sense to go from a very common symptom to a rare disease.
GP doctors are well trained in how to investigate causes and cures. They can point you in the right direction if a specialty is needed to consult.
EDIT TO ADD: If your stomach muscles are normally tight, the first thing I would look into would be emotional stress. The subconscious mind is really powerful, and can definitely tighten muscles, even to the point of pain and disability. Ask yourself what changed three months ago.
