Good you have completed the course in Mechanical Engineering. Since the papers you have completed is also your efforts that made changes and it's possible to clear the backlogs also. This takes time and efforts to consider and know what backlogs you have and how many times you have tried to clear that? If this is due to the carelessness consider this as an opportunity to clear them with a little more marks than passing marks. Make more efforts if there are Maths problems to solve. Solve it again and again in order to keep in touch. Once you have finished college its your efforts with the notes to finish it as quickly as possible. Take the previous notes or the notes from a friend who have obtained more marks, observe the mistakes done by and clear your backlogs.
As much as you put more efforts, the confidence level will be understood and will have a good way to clear those papers. Take a year time to understand the subjects of your strength. Join certified courses with a minimum duration so that you can learn as much as you can while you are also studying for your backlogs.
Try and clear your backlogs within a year. so that you will have a trust upon your own work. Do the hard work and repeat solving problems again and again as the Mechanical Engineering does have statement problems and Math problems. Solve at your convenient times in order to avoid mistakes in the work you do.
Once you have made attempts within six months, the backlogs will get reduced and you can join the dream course of yours. Make a study of the dream course of yours before you enter. Study for the entrance and learn as much as you can. Clear from the first year itself. This will give a way for your career in the future after you have finished your course.
In the mean time take part time jobs and course keep the study habit up. Read books go out with the friends where they have finished their course to know about the future of their also. This will give you guidance if there are any help needed. Your efforts should be more to clear your backlogs.