Clearblue advanced??

How accurate is that test?? I bought it yesterday and it said to test on CD8 with morning urine, well It was CD9 yesterday and it said if you can't use morning Urine hold your pee for 4 hours then use it, so that's what I did and got a big O. Well this morning I got a non flashing smiley which means peak fertility, could I really have gone from no to yes that fast? And isn't CD10 kinda early? I JUST took my last clomid pill yesterday.