If i'm trying to increase my intake by 100 cals a week from 700 to 1800 (eating disorder history) will i gain weight? at 5'2 and healthy 115lbs?

You could: Hopefully you're eating more than 700 calories a week? And even more than 1800 calories a week? If not, i hope you haven't discontinued psychotherapy, and that you're working with a nutritionist. It sounds like you're still very concerned about gaining weight, and may need more assistance as you transition into healthier eating and living. Be well.