PEAK fertility (with no HIGH fertility on the day before) with Clearblue but Low fertility with other brand

I am using the Digital Ovulation test with Dual Hormone Indicator. Since my cicle is not regular (my last period ended on June 1st) I started taking the tests last Monday (June 8th).
Last Wednesday (June 10th) I couldn't get a proper reading with my first urine (there was no result), so I tested again after about 3 hours but I used the same stick and got a PEAK fertility. Since I didn't get any HIGH fertility on the days before I though that this was a false PEAK (also because I didn't hold the urine for 4 hours as advised), so I continued testing, bought a second pack as I ran out of test sticks.

This week on Wednesday (June 17th) I got another PEAK (no HIGH on the days before). I still had the holder from the previous pack, so just to be on the safe side I took another test on Thursday (June 18th) and got PEAK again but on the same day I used a cheap test from Tesco and the result was that I wasn't ovulating.

My question is: should I continue testing? Can I trust the PEAK fertility results I got this week? Why the result on Clearblue was that I was ovulating but with the other brand it wasn't?

Looking forward for an answer, I am going crazy here!!