severe calf cramps, fatigue mucus sore throat waking up in
More information needed
I understand your concern. The symptoms you are currently experiencing may not be related, therefore I need more information to be able to give you an informed opinion.
Severe cramps, in your case, may be a sign of mineral depletion (i.e low calcium or magnesium). When you say "4 bottles of water", how much is that in ml or l? You may be aiming for 2 liters of water per day but if so, I recommend you cut down to 1,5 liters.
Another reason for severe cramps may be inadequate blood supply to your legs due to narrowed arteries. If the cramps occur especially after walking or exercising I recommend you do an ultrasound to rule this out.
Nerve compression is also another possible cause for cramps, especially since you mention back pain, which would indicate spinal stenosis (narrowing of the spinal canal, leading to nerve compression and irritation). Do you also feel pain going down from your lower back to the back of your leg?
I recommend you do with a complete blood test, blood sugar level and a urine test as a first step and I could follow up with the test results.
I hope this helps. Let me know if I can assist your further.