Feeling really dumb

Hey guys! So I'm feeling really lost. People are talking about levels rising etc, how are you even finding out these levels and what are these levels? Like with blood tests or doing it yourself etc?!?! 
Also, I saw that people are speaking about progesterone... Is this a supplement we need to take? 
I literally only just got my BFP a few days ago (1st) and went to the doctor today to get a blood test to confirm it. I just feel so lost now though. Any help would be appreciated!!