Help!

Soo af was coming the 23 I thought thus was the month for sure.. I've had bad cramping, moody, sore breast , but guess who was wrong this girl I got a bfn this morning and then af arrives.. Idk what to do I'm so disappointed .. Idk if my days are messed up on glow or what .. Should I change when af came ?? Deff just feeling like I want to give up I'm so young this should be easy right??!!