hello and welcome to HCM,
I understand your concern regarding respiratory infection and as you opined it is imperative that you will get the flu
Your body pain
and throat pain could be due to the flu itself and also in many respiratory infections you may get blood tinged sputum so you do not need to worry.
You may start a strong antibiotic like the amoxycillin-clavulanate
625mg twice daily after food for five days along with an anti histamine
like levocetrizine 5mg once daily after food for ten days. Your doctor will know about these.
Also do steam inhalation and avoid head bath for the next five days
take only warm fluids and get well soon
If the blood persists or the symptoms worsen, consult an ENT
Dr Sriram Nathan