I do not experience many colds and since I had a bout of bacterial pneumonia in the mid 1990's, I get an annual flu shot. I do take vitamin C when I feel the first hint of a cold. I take 3000-5000 mg a day for 3-5 days and than I stop when the "feeling" is gone.
If you are dealing with colds, flu, and sinus infections back to back, my concern would be "sick house" or local environmental concerns. Have you checked your ventilation duct work for any mold or dust? If you have not, you might change your air filter once a month when it is in use. Newer systems even have a UV Light to help clarify the air. I would also check with an ENT.
The tightness around your calf might be relieved through a good daily stretching. You might also check to see if you are getting sufficient calcium and magnesium and staying well hydrated.
I get pain in my leg along with weakness. Much of this for me is due to the active lesions which are on my t-spine. At least once a year, it looks like the second week of August, I develop pain in my lower back which moves to my left hip, femur, and down to my knees. Below my knees it is often numb to my toes. The attacks on my left leg have weakened it for me and when it is in pain, it is a 10/10 level. I use a heating pad which literally melts my pain away. I place it at the area of the most intense pain and then move it around (Chase the pain).
I hope you can get the answers you need. i am glad you found this site and I hope you feel most welcome.