Young and confused. Help please!

Hi! So I am 19 years old and TTC #1.

AF is 13 days late, and I am having a lot of clear watery/sticky CM. I have taken 3 tests and gotten 3 BFN.

Can someone please help me understand what is going on with my body right now? I feel so uneducated on my body!

Thanks to anyone who can help!