It sounds like you're getting pretty frustrated! Here are some suggestions I give to my own students:
First, set up a study corner without any distractions (no phone, no internet, no siblings), just a cozy beanbag or whatever will make you feel comfortable. Give yourself an hour in there at the same time each day. If you need more time, take a break, then go back to it. Don't stay up late trying to study - it doesn't work.
Keep careful track of what you know and what you don't know. When you come across something you can't figure out, write it down to ask your teacher (or tutor, or parent, whatever).
I used to get dragged down by small mistakes on every math test, until I finally forced myself to go over the whole test a second time. Not just skimming - actually do the problems again. It's really hard to make yourself do it, since you just want to be done with the test, but remember that you're never done with the test...you're just showing what you know whenever a test comes along. If you take the time to go back and find the mistakes you know must be in there, you'll end up happier with the results. Maybe it takes you twice as long to finish a test, but you have the right to demonstrate your knowledge regardless of how long it takes, and your teacher should understand that.
Ask your questions here, too - usually by the time you write out a question, you can figure out how to do it, and if not, someone will help you out pretty quick.
Feel free to message me if you need more help.
Also check out the links for other tips on math problems and focusing.