I was failed as a child, now I keep struggling...

I grew up in poverty and couldn't receive proper education almost all my life (the education system in my country, which is a third world country, is really bad that's why most people resort to international education systems but it isn't always affordable for people that are financially struggling)

So constantly being in and out of school effected me a lot, I was sent to school so late, that I was bullied for not knowing the things my peers did, I couldn't fit in, until middle when I got to attend school for a few years I'd finally made friends but at the end I had to become homeschooled again (as in study by myself because my parents couldn't afford to send me to school) now my peers are graduating highschool and I'm in year 11 struggling with doubt and self worth.

Even though I'm not stupid and don't have much struggle self studying (with the help of online resources) I'm so full of doubt and I constantly worry about the future. Going to a good university felt like the only way out of this cycle of poverty, and now that I'm having doubts about my graduation grades, it's really difficult...

I've been studying 6+ hours every single day for the past few months, yet I struggle with self doubt and worst of all my parents don't have a lot of faith in me, because I used to struggle as a kid when they send me to school because clearly I had no proper educational background... When I see their doubts, asking them to pay for the exams feel difficult because what if... I can't get straight A's, after making them pay so much money? I don't know how I'd live with that guilt.

I know it's unlikely to happen with how much I'm studying but, I'm scared and I'm depressed because I'm so stressed all the time... Life often doesn't feel worth living, but I keep going in hopes of a better future...