Yes it is common symptom,but Not normal.U must consult psychiatrist for medicinal help.
Also Consult psychologist for counselling sessions as this recurring thoughts are very must distressing and u have to face it and fight it.
Health Tips
for overall health
1.sleep 8 hrs at night.
2.avoid too much social media.
3.avoid too much use of mobile pc laptop.
4.avoid mobile pc 1hr before sleep.
5.before sleep may hear good music,or read a good book or can watch a good movie.
6.workout daily or regular morning walk or join gym.
7.Share ur thoughts with ur parents or good friends.
8.Concentrate on ur work,study,passion, hobby.
9.Maintain proper diet.
10.Take proper protein supplement and some time multivitamines.