What could be causing an increase in skeletal muscle CPK levels?

[Mykal1999]

Im a 36 year old male. I work out 3-4 days/week, mostly weightlifting. I've always been on the thinner side with a super high metabolism and I liked to work out to gain a little extra mass. However, I started to notice that my muscles where always sore... this was not the familiar sore feeling from lifting weights, it was more of an exhausted  type soreness. I mentioned it to my doctor during a physical 6 months ago and he tested CPK levels... they came back in the 800s (verified skeletal muscle). I had blood work done again after 1.5 weeks of no exercise and the CPK levels were still in the upper 700s, so my doc referred me to a neurologist. The neuro doc did additional blood tests, which revealed a slightly increased aldolase level of 8.7 U/L. EMG/NCS tests were normal.

I do not take any supplements other than whey protein shakes post workout. I have since switched to a vegetable-based protein shake. I have not really noticed a decrease in strength, although I have plateaued and haven't seen an increase in strength in over a year. I do notice while lifting weights now that the primary muscle that I am focusing on does not get a proper workout because the supporting muscles get tired fast. I have lost about 6 pounds with no change in eating habits and I have lost a considerable amount of mass. Next up is a muscle biopsy.

I also have digestive issues (loose, floating stool; bloating; extremely loud stomach; increased urgency and frequency) and skin issues (thinning skin; veins now showing; skin injuries not healing properly; dry; back/shoulder acne; sensitivity to warm water). These symptoms all showed up around the same time as the muscle issues.