Perhaps thats part of the aftermath vaccination or just you being unwell. Unfortunately you have to go dr to be prescribe with medication. Watson and Guardian pharmacist would not provide medication to pregnant lady. Once you get med, you will be fine. How long? Depend on individual body immunity. After flu vaccine, soon you will be advice to take cough vaccination.
It’s common to get a cold after flu vaccine. Panadol is the safest during pregnancy. But do see a GP and let them know you are pregnant so they will prescribe you appropriate drugs. If not, just hydrate and get sufficient rest for your body to recover on its own! :) get well soon!
Getting mild flu symptoms are side effect of flu jab. Better to ask gynae what medication you can take.