Why have my straight A grades been recently declining slightly?

So for the past few weeks I have been starting to notice that I am getting slightly lower grades than usual on several math and science assignments. I am a 7th grade, all A's, BETA club member that has really been pressured to maintain a high GPA lately. But for some reason, classes that other students seem to be just blowing by like a breeze are rather hard and challenging for me. It seems like the methods to solving things become different everyday and everyone else seems to know it. I have also been bullied A TON recently for my appearance and my higher grades, but I am unsure if that is contributing to this slight decline. While I am still getting all A's, it's hard to be proud of your grades when other children are bragging about their extremely high GPA's and class grades, and it makes my 98 compared to their 100 feel like a 0. I don't know if I'm lacking self confidence or what, but this drop is concerning me, and I want to try to bring it up as much as possible. ANY tips or advice would be greatly appreciated. Thank you for reading, and have a good day.