False positive on clearblue

I just experienced a weird thing. My period is not due yet. On tuesday i randomly checked pregnancy test. I tested using 4-5 different kits (i was paranoid), all showed negative. Ovulation kit shows line but not as dark as control line. Yesterday, i tested ovulation kit, it was as dark as the control line. And so i proceed to take clearblue digital pregnancy test, it showed “Pregnant 1-2”. I tested usingn another pregnancy test, no line. If using calculation, i should by right be atleast 4 weeks pregnant, but we went to W gynae Dr Ben today to scan, seen nothing, which was fine cause too early. And we did HCG, dr ben said my hcg should atleast be 1000+ by now but to my surprised, it showed i wasnt pregnant, the reading is below 0.2 IU/L. You have to be atleast 5 to be pregnant even the earliest. The clinic confirmed i was not pregnant as blood test is very accurate. And no follow up required. So i went back and tested my ovulation and pregnancy kit. Ovulation line is getting lighter, and pregnancy digital was showing “not pregnant”. So im not sure whats happening here. For context, I did not ovulate on the day i suppose to ovulate (i usually ovulate late as my cycle is longer than the normal ones) according to my app calender (premom app which is usually accurate). Or even the few days after i did not ovulate. Confirmed using ovulation strips too. Could it be that im not pregnant but was just ovulating yesterday ? And not sure why the clearblue digital kit picked up the LH surge and shows as pregnant.