Waste a GmatPrep test?

I started my prep about a month ago, only seriously few weeks ago. I took a diagnostic manhattan gmat test and got a 530, 28 quant 35 verbal. But I don't think thats where I am at at all. On the math I didn't know what I was doing, how to manage my time. The questions were harder than the gmat, thereby taking longer to answer the question and therefore I don't know how they are good indicators of the math section. I skipped a ton of questions just to finish and am doing pretty well on math now, I think. I want to see how I'm really doing; I think I'm really in the low 600's right now, but I don't know if i should waste a test to see where my floor score is. My theory was take one now, and since they are adaptive when I take one in a month or two before the test, If I am doing better I really won't see the same questions if there at a higher level- make sense? Any help would be appreciated, thanks.