I need help to get in shape...tired of being heavy!?

Ok first I am 25 and a mother of 4...my youngest being 5 months. After my last baby, due to the birth control i was using... i gained an extra 15 pounds after having him meaning on top of the 20 i gained with him...lol so i am 5 ft 3in..and i weigh about 185...now because of my 4 beautiful kids i am very out of shape...i got that belly flab going on you know the kangaroo pouch...lol its so embring i hate to be undressed in front of my hubby...i really need help! If anyone could me some pointers of how to reduce the flab at least...I do plan to buy a treadmill within the next few weeks so that will help me lose some weight. Is there something I could buy that would be better? Thank you in advance!