Different test kit have different sensitivity levels to detect hcg levels. The timing u pee on the kit matters too. And also as long u see faint line is considered pregnant. As u missed more days of period, the line will get darker.
I would suggest to go to a clinic for a blood test as there are cases where u can be pregnant but ur hcg is low. Let's wait for few more days and test again. I wish the best on ur ttc journey
justamother