My 6mnth baby has had temp ranging from 37.9 to 39.1°c over last few days very unsettled and not feeding as she normally does, advice please. Thanks?

See doctor. Elevation of this type usually comes from an infection.After 3-4 days and no better, see the doctor.
See below. Contact your pediatrician. Some things can only be assessed for during face-to-face contact. I hope your baby feels better.