Respected Madam, I am very sorry to hear about your current mental state and how it is interfering with your academic performance. I can perfectly understand how, at your age, and being unmarried, you can be worried about an intimate experience. It is infact very common among girls who have a similar experience such as yours. However there are two things I would have to warn you about. If you do find these thoughts are unwanted, excessive and keep entering repeatedly into your mind without your permission, it could be an obsession and you would need to consider visiting a psychiatrist for a detailed evaluation in that case. Another thing is, if you find these thoughts or suspicions to be getting worse and causing you to be depressed, please do consult a psychiatrist in that case too. However if you dont seem to have any of these problems, then it would just be a normal adolescent girl fear of pregnancy which should pass with time. Discuss with you girlfriends regarding the situation, and you might find that they too have been in similar situations at some point or not. Just try to get some good sleep, eat a balanced diet, try to find some time for exercise and these alone will help clear your mind. So, Good Luck with your final year exams and Stay Happy