I agree with Sue -- it's such a nice jump I don't know what else could've caused it but ovulation. I guess cd27 would be my second choice but it's a clear second in my mind.
I wanted to add my sympathies on this -- it must be an uncomfortable place. If AF doesn't come soon I'd go get a beta (and have E2 and progesterone measured as well). That could give you an idea of what's going on.
Hang in there, Tracey. I do hope it's a pregnancy that's just not getting picked up that is the cause of all this. It's rare but it does happen.
ttc #3 (#1 for DH)