I just looked at pregnancy charts on FF and the highest BBT seem to be below 38.0. Yours is extremely high. It could be high because you are pg but this seems a little too high - are you defo taking it right or are you ill?
being ill definately affects it, im poorly sick today and mine has shot up, sore throat from hell has made temps shoot up. my highest is always still in the 36's just higher end, 39's are very high