I'd have to echo the PP - have you tracked ovulation to know when you O'd? After years of TTC, I put much more credence in being past your normal luteal phase length than being past your normal cycle length. There are a number of things that can delay ovulation (eg illness, stress) and it's even normal for women to have an annovulatory cycle from time to time - either of these can make your cycle longer.

If you have a repeat bt, ask them to test progesterone. The progesterone level will at least confirm (or deny) that you have O'd.

I'm sorry to hear you find yourself in this state of uncertainty. It's a horrible feeling and I hope you get a resolution soon.