Feel like death first time on it

Hi folks Started on reta to do a few month cut Had my first jab on Friday last week and I feel like absolute death, I’ve had flu and Covid before but this is worse I was coming out of just having flu then having the jab has just amplified it High body temp Constant migraine Fatigue Sore throat High pressure in head and sinus Pain all over Is this normal or possible or am I better getting checked out Its revexa pharma i have opted for