>Used to be fat >Rarely ever got sick >Went on calorie

>>18277580
Stop falling for the conservative propaganda and eat more.

>>Went on calorie restrictive diet
you're probably malnourished if the only thing you were looking at was calories in

in/out is definitely a 100% working solution to weight loss, but it's not a solution for overall health improvements
now you need to look into proper dieting and macronutrient composition

>>18277580
Getting sick, no to mention "sick as hell", every two weeks does not sound normal at all. It probably has nothing to do with the fact that you lost weight either. I imagine you did thousands of other things within that time frame.

>>18277580
Also forgot to say go to the doctor. There might be something seriously wrong with your immune system.

>>18277580
Tip number 1:
Your immune system is dependant on you having enough energy / some fat / rich and good nutrition diet. So if you went under like 20 bmi, you overdid it probably.

Tip 2:
Fat is thermal isolant. When you stopped being fat, your body can get cold much easier and also your blood pressure + hearth rate went down meaning your hands and feet can get cold much easier.

Tip 3:
I havent been ill for ~6 years, then i got three times flu in 2 months. That means you could just get unlucky, changed enviroment or anybody around you got some new type of flu your imune system havent met yet.

Tldr:
Start wearing more layers to keep yourself warm, maybe adopt warm hat on your head and remember it is better to sweat a little than to get cold.

Look at your diet and ask yourself, if you are eating more than tdee and if it is balanced (fats and carbs both present).

And maybe go see doctor.