Pregnancy tests

Hi everyone, I took a pregnancy test on December 19th and got a faint second line! I took that test 3 days before my missed period. I took another on Christmas eve and received a much darker second line which made me feel better. Unfortunately today I took a test and the line was back to being very faint 😭 I am freaking out. Have any of you had the same experience but continued to have a successful pregnancy? Am I definitely having a miscarriage?