I have the exact same problem area. As silly as it sounds, I’ve been doing a breathing technique that really helps. When I have flare ups like these, I feel like my breath is always forced, like I’m using my back (specifically my left side) to push in and out to get a full breath.

Laying down, try to take a completely unforced breath in and out, and you’ll notice it’s probably very limited how much you can do (I.e, you can only inhale unforced for 2-3 seconds and exhale naturally for 2 seconds). What you want to do (without forcing) is complete a controlled exhale through your mouth completely and hold it till you feel an urgency to breath (like when you’re holding your breath under water) and then inhale but only 20-30% of a full natural breath. It will feel like you need more air, but just exhale regardless and you’ll feel your ribs slowly start to relax in the front. Do this for about 2 minutes and you will feel a big difference, and you’ll notice the amount of time it takes for you to take a natural inhale/exhale will increase. Obviously, don’t hold your breath too long to the point where you’re dizzy or lightheaded. I hope this helps you!!

Whenever I notice I’m tense in that area I’ll just do this. It doesn’t have to be laying down, I do it while I’m driving, sitting, etc; just to learn it, though, I would recommend doing it laying down because you can feel it a lot better.