I cannot feel that how much time has passed.What could be the cause?

Can you not tell by the way the sun is changing that time has passed?

This could indicate a medical problem as depression, bipolar disorder, anxiety disorders and schizophrenia can all affect how time is perceived. I would speak to your doctor about it.

Telling time by observing sun light is not sensing time!It is more or less same as telling time from clock.

@anonxd IMHO you should seek professional help. There could be a number of explanations for the symptoms you describe. Thank you for sharing.

The doctors here don’t even listen to your problem,so that they can see more patients.I am a college student and I don’t want to spend money on non beneficial visits.So I am trying to diagnose myself with the help of potential experts on web.
@flutherother Is there any way to be sure that one is suffering from those disorders which you mentioned in your comment?

Please, don’t self diagnose.
You may have some illness, or you may just be tired. No one knows until you ask the doctor.
Going to the doctor is not non beneficial. Go to the doctor at the university clinic if there is one, it should be free, or to the student support service/ the school therapist at the college.They may be able to help you. They are trained and educated to help you.
Asking medical advice on the internet is the worst decision you can make. We’ve no idea who you are, what is your life like, and on top of it all, we’re not doctors. Loosing track of time can be a symptom of anything.

@Sneki95 I said,doctors where I live are non beneficial,I am not talking generally.Sadly,there is no concept of doctors at university clinic here

@anonxd I strongly advise you speak to a doctor about this. It could be important. Your doctor will want to know a lot more information before he can assess what the problem is. eg have these symptoms developed suddenly? Are you on existing medication or taking drugs of any kind? Are you aware of any recent mood changes in yourself or have you experienced a traumatic event lately? There is lots he/she will want to know and they may want to send you for further tests.

I finally found a hack for this! I spend most of my day in front of my laptop’s screen.I have downloaded this Ladybug On Desktop (from http://www.drive-software.com/ladybugondesktop.html) which leaves 5 lady bugs roaming around my screen.They don’t let that part of my mind to turn off which is performs time related functions.Since it is tracking their movement and hence it doesn’t enter sleeping state.There was a cockroach version available as well but they look disgusting.When I need to concentrate more,I can launch it as many times to get more of them on my screen.
I have found a similar app on android that leaves animated lizards on screen.They help me feel that time is passing and that I am not stuck in time.The link to android app is:
https://play.google.com/store/apps/details?id=com.just4fun.lizardinphone&hl=en
I wonder that why they work!