How do I stop feeling like I’ve failed?

It seems like you have a lot on your plate. Try to focus on just one thing at a time. Have a sit down with your parents and explain to them that you're under a lot of pressure, and them putting more pressure on you doesn't help. Try to get a tutor? Remove everything for a day, take a vacation of sorts, figure out what you need to do, and then come back into your life slowly. I hope that helps, I'm here if you want to talk more/need to vent. :)

Try not too let the pressure of others merge into the pressure that you are already putting on yourself. One way to deal with a high work-load is to cut it down into more manageable tasks. Some call it chunking. If you deal with a problem bit by bit instead of trying to tackle it in full-force you will most likely find it more satisfying to fulfill. You need too try and express to your parents the way that they are making you feel, ask them to place themselves in your shoes and see if they would find it fair to be treated that way. Don't give up.