Day 12 spotting on clomid

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Looking for some advice. I am. On 100mg of clomid {after 3 cycles on 50mg} and last month I got a positive opk on day 12 and had a follicle scan. All was good and about to ovulate. I didn't get pregnant. This month I have had no positive opk... Not even a faint 2nd line. I am on day 12 and had some spotting today. My temps make it look like I ovulated days ago but no positive tests. Anyone got any ideas? I never usually spot mid cycle on clomid.