There is really no statistical difference between a 550 and a 570 (and even the actual GMAT has a margin of error of 30 points), so don't sweat it. Also, tests designed by different companies have different algorithms, so your results may not be comparable. I tell my students to think of your exams as a range rather than an exact score; so, you're scoring in the "mid to high 500s".

As for score trajectory, something I see a lot with my students might be something like this:

550 ---> 500 ---> 550 ---> 570 ---> 600 ---> 650

That is, a big drop at the beginning followed by small increases and then big increases at the end. My explanation for this is that it takes time to get used to all of these new things you're learning. At first, your score drops because you're trying to implement lots of new stuff but aren't comfortable with it yet. As your comfort level improves, so does your score.

If you're feeling frustrated, take a few days off. No one says you have you study every day, and sometimes time away from the test can give you perspective and clarity.

Good luck!