I tried Vipassana for some time. I feel some fear of death and reality of life. So what do I want to do? When I do anapanasathi, I feel relaxed.
Vipassana is about seeing things as they are. If you fear death during vipassana meditation then be mindful of the fear. One has to let go of comfort when practicing Vipassana. Anapana leads to temporary comfort, calm and relaxation but one could not become liberated with an anapana practice alone.
Vipassana literally means watching. Buddha wanted you to see your mind. You feel fear because you wanted to run away from death which is perfectly natural. If you feel stress or fear don't run away, accept it as it is and you will come to know that because of your acceptance, fear is vanished. Watch your stress. Just be a watcher. Classifying it as good or bad destroys the very essence of watching. Buddha wanted to get rid of all clinging, good or bad. Just accept it as it is.
The Buddha taught on how to come out of stress. This is systematised in the 4 Noble Truths.
All animals feel the fear of death. This also can be a source of stress.
Vipassana is a an integral part of overcoming stress. So keep up your pratice. Anapana especially creates more calmness and relaxation hence you can try this also. Anapana contains the full 4 foundations of mindfulness hence you can use this as means to liberation. See: ANAPANASATI - MINDFULNESS WITH BREATHING Unveiling the Secrets of Life: a Manual for Serious Beginners by BUDDHADASA BHIKKHU, Right Mindfulness: Memory & Ardency on the Buddhist Path by Thanissaro Bhikkhu
The cravat is to pratice the right way under proper guidance of a teacher. Then you can overcome stress. Wrongly practiced this might create stress. You can try some formally organised courses: http://dhamma.org/, IMC - International Meditation Centre, World Buddhist Directory
I think it will help if you practice a different version of vipassana.Death is not the only form of vipassana so here are some links that will teach you different practices of vipassana.And please note that what you are going through is not a bad side of vipassana,it is simply a matter of choosing the right one for you.once you have done that everything will be fine.
so here are the other forms of vipassana that you could practice without that particular discomfort.
If you feel discomfort while meditating it is better to temporarily meditate "Meththa - The loving kindness meditation".
Learn more about "Abhidhamma" before you practice that discomforting method to understand what life is.
Hope this helped, Click on the blue highlighted words and they will open the links i have given.
Remember the path is not a one full of comfort,it is full of discomfort and hard tasks but each step forward brings much pleasure and freedom that can't be achieved by any other comfortable thing in life.