Leg Weakness and Mobility Issues

Hi! I’m new here and am sharing my situation in hopes one of you have heard of something similar to what I'm going through. For reference, I’m a 23 year old female. Since mid-January, I have been experiencing symptoms in my legs including weakness down both legs, decreased range of motion, and lack of endurance which inhibits my ability to walk distances longer than a minute or stand for a couple minutes without getting fatigued/feeling like I just ran a marathon. As a result, I no longer drive. I also struggle getting down/up from the ground due to decreased range of motion/flexibility and can only go up the stairs one by one with my left leg leading and hold a rail going down one step at a time. These symptoms have significantly impacted my daily life.

Some background is I was having bad anxiety/consistent panic attacks in Dec/start of Jan. In mid January I did a Pilates workout targeting the legs (tons of squat variations including pulsing, calf raises, etc) and I instantly knew I overdid it when my legs were shaky and stairs were tough right after. It became extreme DOMS, I had a heavy sensation as if bricks were weighing my legs down, and even lightly pressing my legs hurt. Probably irrelevant but I also got a really bad cold around that time. It’s as if my body freaked out with everything and somehow turned the DOMS into weakness that never got better.

Since then, I have seen a neurologist, rheumatologist, orthopedic dr., musculoskeletal dr., and primary and urgent care. All are stumped and don’t know what’s going on, saying it’s an unusual presentation and weird I have no other symptoms.

I have had an MRI on my lumbar spine and brain which were both clean and rule out MS. My EMG/nerve conduction came back normal. I have gotten lots of blood drawn 4 different times and everything is in normal range. From my autoimmune blood panel, only my ANA was positive (abnormal), but my neurologist said women often are positive even though they don’t have autoimmune disease. Mine was a speckled pattern and titer was only 1:80.

Since mid-February, I have been going to physical therapy 1-2 times a week and have seen slow, small improvements, but still not close to where I was before all this.

Since I struggle with walking a normal pace/cannot walk far before my legs feel completely wiped out, I only average about 1,000 steps a day if even, and my legs (especially my right which is worse), have visible muscle atrophy.

Any thoughts/suspicions on what's going on? Could my symptoms simply be caused by lack of use and get better if I gradually start moving or have someone stretch my legs each day? Or is it some rare autoimmune disease that got triggered from the leg workout/bad anxiety I was dealing with in January? Or does it sounds more like a muscular condition? Thank you in advance, I just want my life back.