Heard about body temperature going up when fertile?

It does. A bbt(basal body temperature) chart can often tell when the second female hormone Progesterone has been released as it is thermogenic(heat producing) and comes from the corpus luteum(yellow body) of the ovary only after ovulation.
Temp up after fertil. The basal body temperature ( temp in the am after a 6 hour sleep) raises by about 1 degree after ovulation. Once the temp has gone up it means that the egg was released about 24 hours ago and you missed the fertile window. Only way to tell in advance is the ovulation predictor kit that tests for lh surge which is 24-48 hours prior to ovulation.