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Hello, I'm Dr Manos, M.D., board certified ObGyn. It's very possible that your upper respiratory infection caused enough stress that the hypothalamus area of the brain that controls the pituitary gland was affected by the stress. Ovulation might be suppressed altogether or at least delayed. For now, you'll have to wait and see what happens to your cycle. You might even have some spotting.
On top of what I said, you got a shot of decadron which is a steroid and will also affect the pituitary. At least you were regular since stopping bcp's so you should be regular once all these factors pass. All this is common with women not on bcp's.