Unity is slow while ran normal before

hi this is my first post,I am a begineer in unity so I strugle with it a lot so my knowledge of it is very low

so I might find my problem dificult to explain

the problem is that unity runs very slow,practically unusable and I dont have ide why cuz it ran normal before

but when I press play the game runs normal,though at the beggining very low but quickly goes to normal speed but tend to "stutter" or slowdown sometimes,so I just dont have idea

I m using unity 5.4.3 my pc specs: Sony vio e series

windows 7 ultimate 64bit

Intel core i5 3210m 2.50 Ghz

4 gb ram

Amd radeon 7650m

Plzz help me