Advice needed

So it is the early morning of the 15th. Still no AF, temp came back up a little today (to 97.8) but I also only had 4 hours of sleep. Dr. O.T. said this was the day for the beta, but I don't know if this is too early. I am 15dpiui, I'm guessing 13dpo. I know I could still get a false negative if I POAS, but is this an appropriate time for b/w?

I have decided to not go back to this doctor for further treatment. As I have said, I work with him and I see how he treats his patients - without much regard usually. I have seen him cut an episiotomy on a women who was yelling "you're not going to cut me are you?" His latest shenanigans have involved a medical review of a case. He is so close to retirement he can smell it and I think he is mentally checked out. Now, he used to teach at Georgetown, and he has been an OB for 45 years - he's no slouch, and I actually really like him during casual conversation. I just think he has his own agenda when it comes to patient care and I no longer want to put the fate of my pregnancy in his hands. SO, my appointment with the RE is Sept 12. I think we will probably take this cycle off - but I am worried about not temping, worried that I would be losing some bit of vital information for our next step. For those of you who have done IUIs - what kind of importance does your RE place on bbt?