Yes you defiantly have a power supply issue:-
when i connect two servos and one Ultrasonic sensor it gets disconnected every second from the system,
That is supply a decoupling issue, the servos generate interference that resets the processor. You need to add some isolation to the servo feed like is described here:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
but when i use it using Adapter, it slightly turns and doesn't move at all.
The adapter can not supply enough current for you bot.