Hello,

First of all, there's no point in dwelling about your past scores, because you cannot change it.

Secondly, if you have decided for once and all , to go ahead with your higher studies, then focus on XAT and MAT, for that matter, since unlike CAT, these exams do not have set any eligibility criteria for appearing in their exams. Your determination need to be strong for this, because this is only what will sail you through all this.Moreover, there are many instances, when people have done extremely well in not just in entrance exams, or business school, even professional career for that matter in  spite of not so good marks in past academics, but does it mean, it all comes easy, absolutely not. You'll have to work hard and focus on what's important right now, that your entrance test, Follow your syllabus, practice previous year papers and sample papers, you can judge yourself, how you're faring, moreover this will also gain your confidence in the time to give exams.

All the best!