Hi smrishar,
GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability. The 4 Official Scores that you reported (630, 590, 570 and 580) show that you essentially performed the same each time (about 600 +/- a few points). You handle certain aspects of the GMAT consistently well, but you also make certain consistent mistakes. Raising a 600 to the point that you could consistently score 740+ will likely require at least another 3 months of consistent, guided study - and you'll have to make significant improvements to how you handle BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. Assuming that you studied in an efficient fashion for the next 3 months, you might look at the end of May as a reasonable estimate for when you might take your next Official GMAT.
GMAT assassins aren't born, they're made,
Rich