Financial talk

i'm 5'3" & up until a few months ago, i'd always been between 125lbs and 130lbs, no more, no less. but in the past few months i've been gaining weight like crazy, and am now almost 150lbs (!) i believe it's because recently i've gotten a car and now drive everywhere (i used to walk everywhere before), and restaurants are more accessible. plus stress from classes and work and r'ship problems have been making me eat more. i want to work out and everything, but dont have money for a gym membership, and not a lot of time either. what can i do to start getting back in shape? what are some foods i can shop for that are both healthy and inexpensive? thanks for answering and being polite =)