Honestly, math is an uphill struggle for some and a breeze for others. Don't blame yourself - you might just not be a natural in this department. When you get the answers wrong constantly, then you need to stop practicing the questions. Take a short break (5-10 mins, calm yourself and focus), and then reread the example material or talk through the problems with your teachers. If you're struggling with questions, don't keep trying them. You need to work out:
-What you can do.
-What you can sometimes do.
-What you are unable to do. Work out where the basic problems have arisen, and nip them in the bud. Get your teachers to go over bits with you in their lunch hour - it's their job; they're paid to do that.
If you can get 75% of the questions right, then ask a few here on MHF and we'll see what we can do. Don't try and tackle too much content at once, also. Take it in bitesized chunks.
Never be afraid to ask your peers for help. Often, students can convey the material better than teachers because teachers have a tendency to overcomplicate things or to explain things in ways which are very accurate and precise and very confusing. You could arrange for a study group or something, although I think that's unlikely to succeed (and it's tacky!).
Otherwise, it really is just about persistence. Get sleep, stay hydrated, and don't be disheartened.
Edit: I forgot to say, for my applied course, I had a teacher that did the whole '5 spur-of-the-moment questions' thing - what a terrible teaching style! I don't know why it's favoured. It just puts people in a panic and disheartens them, making them more likely to slip up. I hate it with a vivid passion. The way to deal with it, I found, was to pretend to take notes while the teacher is looking for someone to ask - it doesn't always work, but it will help!