Hello student ,

First of all there is no need to worry and the point that you have to remember is that you can't leave any subject weak. You have to study all the 3 subjects .And as you said that your physics is weak then try to give some extra hours in solving numericals . For more than 550,you have to score more than 300 out of 360 in biology . And for physics instead of just memorizing the formulas, understand how that formula came, means understand the derivation. Understand the steps and variations in different questions . Beside this if you have joined a coaching class then take all the tests regularly and don't miss the tests . And important thing keep solving mcq and previous year question papers .

Hope it helps !