Hello

First of all, ask yourself are you interested to make your career in the science stream. if not then just change your course and do what you like to do, which makes you happy. because next 39-40 years you have to continue the same area course so, you should be happy with that.

After all these you think you are interested in the science stream then

1. Wake up.
2. Find the best college you can get into. And if that includes giving other exams. Prepare for them.
3. Get into college.
4. Jot down the skill sets you to want to have and start building them.

You have other options available as well like graphics design, mass communication, BCA, animation etc .you can go to any one of them. These all fields have good scope.

Note - marks are just a matter of paper so relax and take your time and think about your future.

Good luck