I think with residual hormones in your system, there's just no way to know what your body will do. You only recognize temp shifts after the fact (if you have temped for a really long time and know what your normal temps are, you might suspect when a rise has just happened, but to confirm O, you need 3 high temps so you still have to wait for that. Temps can also rise for reasons other than O - illness, stress, disturbed sleep, etc.) You're going to need to use a back-up barrier method for quite a while - I don't think I'd have unprotected sex at all right now if I were you.
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