What you did first semester isn’t working. First things first, fess up to your mom, right now. The longer you leave it, the worse you are going to feel. Rip off the bandaid and get that over with. Yes, she’ll be disappointed. But she’ll still love you, and she will be far more concerned that you felt you couldn’t tell her. As a parent, I know this is true. I’d far rather know that you are having hard time, because maybe I can help you, even if it’s only to say “I love you and I understand how you feel. I support you no matter what.”
Secondly, you need to do what @bopper suggested. It’s called earning a degree for a reason. You delay physics and do whatever you must do to get your GPA up. Tutoring center, office hours, doing all the reading, doing all the assignments, studying a lot, and playing when the other stuff is done. PRIORITIZE your education. You might have a tough semester. At least it will be less tough than feeling badly about yourself. Good luck.