Hey Jillnicole! I feel your pain and frustration and I really feel for you. You are in a tough situation because you are constantly surrounded by temptation. For you, it will have to take a monumental effort to avoid those things...but it CAN be done! You know what to do to lose weight beause you have done it...now, it's a matter of getting your head in the right place.
First, you say you walk every night. How much do you walk? Could you do more? Could you plug some jogging into it? Sprinting and walking is great for weight loss. Second....you can buy foods that are healthy and inexpensive. You just need to stick to it and for when the others are scarfing down chips and soda, you could munch on carrots, and frozen grapes (my favorite).
The thing I like about calorie counting (which is what I'm doing) is that nothing is truly off limits....you just have to make it portion controlled. Also, I would highly recommend that you keep a food journal...just for a little while. It might give you an extra sense of control.
Finally, if you're drinking any soda...I suggest you quit. It took me several attempts to quit Diet Coke, but it helped me get rid of many migraines and it helped me control my appetite too.
If your friends are really your friends, maybe you could talk to them about buying helathier items...or at least tell them not to give you any junk.
It's hard to give advice on these matters. You gotta make a decision that you will stop right now. Stop hurting yourself. I know how it is to gain weight back. I have done it, so I really do get it. I just think you need to switch things around to make this work and to know that it's never hopeless. You have the power of choice.
Hugs to you!