Afraid to gain weight

I notice that everytime I have a little weight fluctuation, if I gain a little or I lose a little, I tend to freak out. If I’m losing weight, I’m afraid to lose too much and not be healthy, and if I gain some, I’m afraid to lose control and get fat.

I think it’s partly because I have a chronic illness that have led me to loose a lot of weight rapidly in the past, and then have medication that made me gain a lot as quickly. However, all of that is in the past : my illness has been under control for years now and I’m naturally skinny, so I’m also judging myself for worrying about this non-issue. How can I break out of this pattern and just enjoy my body?