Ugh it's horrible being ill when pregnant. My only advice would be lots of fluids, take paracetamol, and get checked by GP/ midwife for UTI just in case. Probably just a bad cold/flu but I felt like I had flu minus the snot and cough for about 3-4 weeks and I finally found out it was a silent UTI which is really common in pregnancy apparently.
A high temp over 38 can effect baby in later pregnancy (make baby have a high heart rate) as I was listening in to the consultant at the hospital yest advising a lady. So not sure about your stage of pregnancy. I would phone up nhs and ask for advice.