Welcome to Healthcare Magic.
Your symptoms are quite sparse and does seem to indicate a serious underlying illness.
You should get evaluated by a local physician and get investigated.
The swelling in one leg may be indicative of something sinister like deep vein thrombosis
or a malignancy.
A lower limb Doppler should be done urgently blood work up for coagulation and infection should also be done simultaneously.
The treatment should be started according to cause as soon as possible.
I hope the advise will be helpful for you.