Don’t worry! It won’t affect your baby. I was sick every month during my second and third trimester. Just make sure you do not self medicate. Take pregnancy safe medication from doctor. My gynae told me to rest more, drink more water and take vitamin C to boost immune system. It’s normal for immune system to be weaker during pregnancy.
This one better not wait please see your gynaecologist or A&E now, even if it's early. A fever that lasts this long in pregnancy needs proper checking to make sure baby is okay, and your doctor needs to know what's going on. Please don't delay just because it's still very early on.