Sometimes mobilization of the fascia is necessary before the scalenes really want to stretch. I'd check for an ASTYM/Graston technique provider in your area, but massage (and not just dinky stuff) should be tried too.
Fascia and scar tissue are two things that have troubled me greatly. I personally think that MDMA can contribute to excess fascia type tissue due to its activation of a serotonin receptor 5HT2B that causes differentiation of cells that produce collagen called fibroblasts - this is known to be the mechanism of MDMA induced cardiac fibrosis.
One study showed about 30% of heavy MDMA users (I think the lifetime average was like above 500 uses) met criteria for different heart conditions, some 30% had valvular heart disease of the various valves. If it is within your means and you were on the heavy side of MDMA abuse I would consider pursuing an echocardiogram to check for valvular heart disease. I can produce the study concerning MDMA and cardiac fibrosis if you like, but I am mostly mentioning this not because I think you have valvular heart disease but rather just to impress upon you that it is possible that MDMA stimulates fibrosis of tissues, so tissue mobilization techniques are probably important.
If you weren't a heavy user of MDMA I wouldn't worry about the heart disease thing, and definitely don't let it stop you from exercising - if anything let it motivate you to increase the strength of your heart with cardio. I was previously convinced I had valular heart disease (and I was a really heavy abuser) but now I don't think so because of how much improvement I noticed with long term cardio.
What would you say your lifetime usage of MDMA was? More than 100 times or at pretty high doses? Any use of psychedelics like mushrooms? Did you take a lot of 5HTP? Just curious.