Ya know what? I think that what your going thru is normal... we all hit that point where, in our heads, theres this tiiinnnny voice that says- you can't do this! Give up now! Well, thats a total crock. You've already come this far Natalie. You know exactly what to do. Look at the success you've already had, and tell yourself it'll keep comin if you let it. I hate exercising, as well as a lot of people, and I don't have arthritis like you do, but ya can't let it stand in your way. Even if your at your bf's house, get your butt out the door and take a stroll. Doesn't have to be a long one, doesn't even hafta be strenuous. Use it to clear your head, use it to fight a craving, anything! Make him come with you... I'm kickin your butt here, chica, get to it!!
Don't give up, and walk away from the skinny peoples food. Think of it this way: You are showing tremendous strength by eating healthy, and in the process you are working to eliminate future and/or current health problems. They keep eating that crap- well- they'll be fat someday. Its a fact that the older you get, the less your body works for ya

show em whos boss here. You got this!