Surronded By Lots, Yet Very Lonely

Hello there... I'm a 16 year old girl, I just needed to share my story. My dad passed away 3 years ago. He was the person I loved the most, the one I shared my days with. Since he passed, my whole world has changed. I started questionning life, wondering stuff I would've never think of... I'm lost. Moreover, my mom has a new boyfriend. I do want her to be happy, but I just haven't finished grieving and it's so hard. I have lots of friends and a big family but I'm the center of this family, the strong one, I can't tell anyone about my insecurities... I want to make my dad proud of me but I keep failing everything I do, my grades are getting worse. Lately, my mom has been telling me over and over again she wishes she died too because it's too hard for her living with me and my family, it hurts so bad, she can't even imagine how her opinion is important to me... I'm just lost, I just needed to write down what I feel. Can anyone help?