He has lost confidence in himself. Help.

My husband was alright since 6-5 months he's a bit disturbed. He has lost weight as well and looks too dull. He tries to avoid the crowd and very little interaction with the family. He works in a corporate sector and for the past 2 months his work load has reached to peak. He is losing confidence in himself and its visible in is body language.. By the way he walks, talks.. Im really worried. He tries to escape any important discussion. He's not happy with his job.. Its too hectic for him. He's planning to quit his job in june or july,and start up a business of his own, but he's not sure if he sould really quit now because we're getting married in november. He's not able to sleep well, sometimes he skips  meals, he has started to smoke alot. He tries to quit, but he's not able to do so. Im really worried about him. Please help.