What is this toothache - grinding pain, TMJ or something more?

[Andrew20]

At the end of last year, I have root canal on my premolar and the back 2 molars removed on the lower right side. Since then, I was diagnosed with mild TMJ where my jaw on the left side pops out at night (and I can usually wiggle it back in in the morning) or I get a sore tightening of the muscle between the jaw and cheekbone - also on the left. I have an achy jaw and tender jaw joint on the right. This doesn't really bother me too much, the problem is, I also have an ache in the 2nd from last tooth on the top on both the left and right sides on and off. I have had these teeth checked by my dentist a few times (x-ray, percussion, sensitivity) and she can see nothing wrong with the teeth. The pain alternates between either side and I never have it on both sides at the same time / same day. For that reason my dentist thinks it due to me clenching / grinding my teeth as its hopping from tooth to tooth. This has been ongoing for the last 6 weeks and it driving me mad. Ive had daily pain on one or other side each day. There is no stimulus I can point to that brings on the ache - I can eat and drink hot or cold without any immediate or shooting pain or sensitivity and it usually lasts from mid morning until the afternoon. My question is, is this typical of grinding tooth pain and if my dentist cant see anything wrong, is there else can I turn to try and sort this or do I just accept its grinding pain? I have a mouthguard for the last week to see if that helps but I cant say it has helped just yet.