When does a fever become a concern in pregnancy?

[{sarah}]

I've been feeling a bit off all day & now I am sitting with the aircon on, knowing it is still hot (37deg outside) but have goose bumps and am shivering. I checked & my temp is at 38deg so slightly elevated, but nothing severe as yet. What sort of a temp is a concern in pregnancy & what should I do? Same stuff as babies, tepid shower, limited clothing, panadol... I have a headache (which isn't unusual for me) and feel nauseaus as well, otherwise all good.