Hi Aayush!

First, please stop worrying about how you aren't able to concentrate. 

If you work properly, you can easily pass biology since this is a theory based subject and you don't have to do complex calculations. The trick with biology is that you must just learn the whole thing by heart.

You have many days, you can easily do it. Let's see you have 20 chapters to learn, then divide your days accordingly, even if you learn a chapter a day, you will still manage. But, the most important thing is revision. Whatever you learn on day 1 should be revised on day 2. Revision is the key here, revise, revise and revise. You must complete at least two revisions before the exams. Don't leave any chapter completely to revise at last, you won't remember anything. Set aside some time for revisions everyday. 

I am sure that if you do these things, you will definitely pass your exam and that too with flying colours.

Good luck!