What could be causing upper shin and calf weakness? it seems to become worse when i'm barefoot or after i've taken a shower

Leg weakness: If both legs are involved I would check for a peripheral neuropathy. If more diffuse muscle weakness is present deficiencies of calcium, magnesium, potassium,thyroid are possibilities. If symptoms persist I recommend an evaluation by a neurologist to look for neuromuscular disorders.. Appropriate tests will be ordered.

Varies: There are numerous possibilities, from benign disorders such as Tendonitis to severe neuromuscular disorders. I would not hesitate to be seen. An exam and appropriate studies would likely yield the diagnosis.