I get very sick to my stomach if I eat or drink anything with Aspartame in it, and it will trigger migraines too. I'm very careful to read the labels on food/beverage products that I buy to watch out for that.
I live with chronic pain issues because of cancer, so I can totally relate to having my pain worsen because of the weather. I had the issues with Aspartame long before I had cancer. I hope your pain eases up soon!