Has anyone physically crashed on Vyvanse?

I started Adderall XR last October then switched to Vyvanse in December. At first I felt like it helped SO much. Emotional regulation, a bit more energy, ability to focus! But since then, my physical health has gone downhill so much.

I was always low energy before but I could do a workout every day (30-60 minutes weight lifting and Pilates) feel tired, but rebound a bit. Since a month or so after starting Vyvanse I’ve gone downhill in my ability to workout to where even a morning walk exhausts me. I can’t do a workout without physically crashing, 0 energy and need to lie down to recover for an hour or two after. I’ve worked with an endocrinologist who checked my adrenals and everything and said everything is normal. My cardiologist has suggested chronic fatigue syndrome but it’s a diagnosis of exclusion and we’re not there yet.

I’ve never had the best health and I am being treated for POTS and so have an autoimmune disease that’s mostly been dormant so I know it could be unrelated but I’ve also had the POTS and AI for years and the timeline of a steady downhill for almost a year now since starting Vyvanse really has me wondering if that’s why. I’ve had flares of intense fatigue and brain fog before but none that have lasted this long, usually just a few weeks.

I’m self employed and have little kids so I’m now scared to go off Vyvanse. The times I’ve missed a dose I’m so brain foggy and unmotivated and just exhausted I’m not functional at work or as a parent. If I go off Vyvanse I don’t know how long it will take for my system to re-regulate and I genuinely don’t know how to manage that with kids. And what if it doesn’t help and I’m just even more exhausted??

Anyway, has anyone else experienced anything like this on Vyvanse? Is it possible it could be the cause? Did anything else help?