Aw, lika mo na talaga sa pregnancy yan, pero since 20 weeks ka na at may lagnat, mas better kung mag-check ka na sa OB mo para ma-confirm kung normal lang or may infection na need treatment, mas safe para sa baby. In the meantime, drink lots of fluids, rest as much as you can, at try lukewarm baths or wet compress sa forehead, pero huwag mag-take ng meds on your own kasi maraming hindi safe habang buntis.