mic work when I keep pressing speaker with thumb

hi , please help me with my problem

i have iphone 4 and its mic not working

the problem is wenever i make a call (without headset and with headset ) , we cant hear each other. but when during call i press on right side of ear speaker hardly ,

we both can hear each other clearly.

so m sure my mic and audio chip is gud.

also i have cleaned the tiny mic above.

my guess is something wrong with speaker or its connector .

please tell if am right or not coz i just opened battery cover of my iphone (for first time )

also what mite be the faulty part (if any other )

thanks in advance