The most important thing is not to panic. There is still ample time for you to address the gaps in your preparation for the Board examination.
It is quite natural to feel a little anxious about your preparation, especially when you are paying attention to the AI PMT and the Class XII Board examination simultaneously. From what you have stated it is clear that you are aware of the areas that need your focused attention at this stage and it is a big plus for you. All you need now is a workable plan for time management.
You must firmly decide that you will give your undivided attention to the Class XII Board examinations. Then prepare a work schedule giving priority to lessons in different subjects that you have not yet prepared.
As you read them, make notes in writing; which will help enormously in retaining the concepts in your memory and for recapitulation later. Try to follow your schedule as per your priority and set aside about an hour each day to make up for any shortfall in meeting the requirements of your work schedule.
Re-visit the lessons you have already learnt and revise them in a phased manner. Be positive and spend some time articulating the concepts you have learnt with your friends or teachers. It will help in reinforcement and concept clarification. Also remember that all work and no play leads to boredom and monotony. Go for evening walks and spend some time in the mornings for mild exercises and meditation.