Exhaustion. Hotter or i'm very sick.

You might have electrolyte imbalance due to dehydration. Since you have all blood tests normal, and your symptoms seem to worsen in hot weather, it can be due to dehydration. When you are dehydrated, the natural balance of electrolytes in body is disturbed and things like low potassium can cause muscle weakness. This is why you might be feeling vague body aches. Try consuming electrolyte rich fluids like coconut water, lemon water with salt and sugar. Sports drinks like gatorade can also help. Besides this, take regular meals and avoid too much coffee and tea. Some clues that you are dehydrated include passing very less and high colored urine and having dry lips and skin. If you feel more tired after you wake up, get evaluated for sleep apnea.

Avoid alcohol and smoking if it applies to you.