Plan B terrible side affects

had unprotected sex for my first time and took the morning after pill within 12 hours the next day and at first i was nauseas for two hrs which i knew was common but three days later i woke up with a fever and all the side affects. went to the walk in and they said to just rest and take panadol but i’m really worried that it’s now been almost 5 days since i took the pill. how long to side affects last???