Im so confused help!

So last night i was 5 days before my missed period, took a test and it was a faint Positive (First Respone Curved), then i took two more of the same kind this morning, and it was a suuuuuper super faint positive. But when i took a Dollar tree test, and Clearblue Easy Digital, it said not pregnant. Could i be pregnant, or not? Did the first response tests just detect it earlier than the other ones could?