Hi Anushka,
Don't let down yourself by doubting your abilities. We may have some weakness in some areas while preparation but correcting those mistakes and rising above from current level makes us confident. So, spend some time for identifying and organizing your strengths and weaknesses on the paper and post it in the forum before taking decision about scheduling your exam. There are really good experts available in the forum e.g. EmpowerGMATRich, Targettestprepscott, BB, chetan2u, VeritasKarishma, GMATNinja and some others, who can help you to map your way to success in the GMAT.
Official Mock are considered closest to the real GMAT, so you can prefer those.
Have faith in yourself that you can do it. All the best for your journey to the top B-school!!!
Regards,
Raxit T.