I solved the problem.It was because
1. it wasn't able to Remount the root directory as read and write after fsck used it as read only at boot time for that I did
sudo mount -o remount,rw /sda1
2. it wasn't able to display the desktop because lightdm service was stopped and for that I did
sudo service lightdm start
Well for now it is working perfectly.I don't know there may be a better solution.Any way thank you so much for your help.I am going to try to install and configure additional kernel.I hope u will be there to help me if I come across a problem as usual.