Hahaha I read the title and was like Oh... this is gonna be good! lol
What's sad is that a lot of people don't know better and will believe whatever their doctors tell them. My friend, for example, was 15 weeks pregnant (or so) and the doctor told her the baby is probably going to be too big to deliver vaginally and she'll likely need a c-section. Really?!?! It's 15 weeks, you have no idea how big that baby'll be!
hijacking this thread to say wow re: the 15 weeks story. First of all, given that doctors date pregnancies with lmp (not ovulation--and they don't even listen to you when you tell them your o date), they could just have the due date wrong. Second, so much can change! When I had my 20 wk ultrasound, DS was in the 95th percentile for length and weight. He was born on time at 6lbs, way under average.
As for the OP, the doctor was probably referring to how the temp goes up after you ovulate (so it's useless at that point) and opks will tell you when you are fertile and it's a good time to have sex. That being said, I COMPLETELY agree wtih you. In fact, if I had to rely on one vs the other I'd go with temping.