Help please??

So I figured out how the tests work but confused about my results I’ve been testing for almost three weeks now and have had low levels my husband and I had sex Tuesday morning I checked Monday night negative checked Tuesday afternoon and evening positive app says almost there to try and then today nothing took several tests and there is barely a line the other ones were way darker and almost the same color how is this possible all the signs are there cramping and lower back pain I also have egg white mucus not sure if anyone has had this ??? I already took several pregnancy tests the hcg strips had faint lines I then got more pink dye one to check again and they were neg