Hi Peichen,
With a late-April Test Date, you have plenty of time to study and improve your Quant scores. With a Q44, you likely did really well on the 'math' questions that you faced on Test Day, but you missed out on lots of the 'strategy points' in the Quant section. However you choose to continue to study, you should plan to focus on Tactics, pattern-matching, etc. Based on everything that you've described, I think that you would find the EMPOWERgmat Quant Score Booster to be quite helpful. Most of our clients complete that Study Plan in under a month, so the time commitment wouldn't be too intense. We have a variety of free resources on our site (
www.empowergmat.com), so you can 'test out' the Course before setting up an account.
GMAT assassins aren't born, they're made,
Rich