Same ole story, just a different day

Hi
I've been religiously logging all food and exercise. According to MFP, I have a calorie deficit of 700 calories and should be losing 1.5 lbs a week. Some weeks, I'm down a little, some weeks up a little. I've gotten very discouraged, overall. I don't always eatback all my exercise calories. I've been underestimating my exercise calories, being afraid that I'm overcalculating.
I'm type 1 diabetic, with hypothyroidism. I try to comprehend the idea of eating more to lose, but can't seem to wrap my head around the concept for long, for fear of gaining it all back.
I know this is the same ole, same ole for all of you. But, I'd love some feedback. Thank you in advance.