It's hard to tell from the test score what your "true level" is in either V or Q, because your pacing will have had a dramatic effect on your score. It's good to discover that early, and the good news is you can improve pacing a lot, especially in Quant. You might be experiencing pacing issues for one of two reasons (or a combination of the two) --
• you might be investing far too much time in certain individual questions during the test, leaving you too little time to finish
• you might generally be using slow methods to solve GMAT questions
The first issue above is one you can improve at with test-taking practice. Almost no matter what your level, adaptive tests will get harder and harder until the questions are too hard for you. You're not even supposed to get those extremely hard questions right, and if you get them wrong, that barely hurts your score. What will hurt, however, is investing a lot of time in those questions. So if this might be the issue, on your next diagnostic, I'd suggest you try to move on much more quickly from Quant questions when you don't quickly see a path to a solution. If after about a minute, you aren't sure how to get to an answer, quickly evaluate any fallback strategies (estimation, say), and then move on, saving your time for situations where you can tell a time investment will be rewarded.
If instead you think the second issue might be relevant, then you may need to learn different ways to approach GMAT math questions. My higher-level GMAT math books teach faster methods than any prep company materials teach, and if you might be interested in buying any of those, feel free to contact me at the email address in my signature.
But for now, I wouldn't suggest taking another diagnostic test immediately. Instead, I'd move on to timed practice, using official questions, so you can diagnose your timing issues. If you find you're solving most questions reasonably quickly, then you're probably experiencing pacing issues only because you need to be more disciplined about moving on from difficult questions mid-test. If instead you're spending 3+ minutes to solve many questions, then you probably need to find ways to speed up in general. Keep in mind that a 4+ minute solution to a GMAT question isn't really a solution at all, because you're actually hurting your score if you spend that long on a question, unless you know you can spare the time.
Verbal pacing is a trickier issue, and it would be best to seek advice from a Verbal specialist about it (I'm a high-level Quant specialist). Good luck!