I guess it "could" be stress related, but unless you have some real definite ongoing issue around you causing that kind of stress, it's doubtful.

I wuld put my bets on toxicity of some kind. Toxins can be in the gut/ kidneys/liver and cause a feeling of weight, heaviness and tension. Hard to explain, but an ongoing source of toxicity is likely to collect in those areas, anywhere in fact.

Even toxins in the brain can affect the body, so its 'really hard to know where the toxins are at the time. LIke gut toxicity can cause mental symptoms and vice versa.

Like with myself, I now have severe gut problems, like a feeling of something being clenched, and I also get the strange feeling of a weight/heaviness around the middle. I cannot explain it, I don't have the words for it. This start much more when I had dental work done in 2004, which was 2 composites redone (which could be leaky), and wisdom teeth removal (could have cavitations). So it's really hard to know what's doing it and how.

With mercury/candida, I have also had a weird lower back tension, almost pain. I think they call that part the ganglia, but I maybe wrong. It used to drive me nuts sometimes.

So over the years, depending on the toxiicty, I have had some weird issues of that sort and unable to really explain it. Now upon exposure to toxins or from trying to eliminate toxins, I can end up those toxins going straight into my gut and this causes me great distress because they remain there and cause ongoing pain and other symptoms. This never used to happen, but since 2004, it's been a constand problem. I do not know what is doing it.

Magnesium may help you with these odd sensations going on. If it's muscle related, it should help. Calcium and magnesium both. Toxicity can deplete this very easily and they are needed desperately. Muscle tension or other odd muscle sensations or feelings could be a sign of mineral depletion. You may find magnesium/calcium are helpful.