Sketch Problem

Hi, I am a new memeber of this forum. Previously when i did drawing in solidworks, if i move my cursor to previously drawn circle then it can detect the centre automatically but now it can not. so i have to do it by myself, but i think it is very difficult to detect the center or any endpoint of any solid line.Can anyone pls suggest about this problem, ur suggestion will be highly appeciated. Thank u.

SolidworksSketching