Hi. I had this problem on Clomid one month and I am pretty sure that I ovulate on my own as well. For two months, my gyn (before we started seeing an RE) wanted me to try Clomid b/c it helped us conceive DD, and that happened to me with my temps. They were all over the place. I didn't know if something weird happened that month or if I just didn't ouvlate at all that month. I kind of felt like the Clomid messed up my hormones or something b/c I had bad hot flashes and other side effects.
Although, I do agree with Kathy, if you didn't sleep well, you temps would be likely to be off. I have had that happen as well. Anytime that I don't sleep well, my temp seems to be higher. BBT'ing is a frustrating thing. The longer that I have been doing, the less stock I tend to put into them. But, I still do it b/c I am so used to it and b/c I am irregular so it really helps me to get a general idea about where I am in my cycle.
Good luck to you. I would just start now TTC and do it every other night until your temps go up and stay up for at least three days.
Anna Leigh