Niva also don't forget that you can have a triphasic pattern and not be pregnant, and not have one and be pregnant. My pattern last month was triphasic and I was convinced I was UTD until AF arrived.
It's not looking like I'm going to have a 28 day cycle this month. Not even a shadow on an OPK yet, so I think it could be a CD21 O like it was for DS - assuming I actually O, I worked out when we were trying for DS that two thirds of my cycles are anovulatory which sucks.