Does anyone have experience with this??

Hi everyone, first time poster looking for a little advice! I recently have been doing weekly 36-48 hour water fasts. I mostly do these because I have stomach issues and I like to "clear out" my GI tract. It really has been a help thus far and I've been experiencing less problems with IBS and my ulcerative colitis. I would like to try a longer fast just to see how long I can go and test my body pre and post autophagy. However I have a few issues/fears regarding longer fasts: - I am kind of scared about how the refeed period after an extended fast will affect my stomach. My body is very sensitive to adding and removing foods (ie. I don't have something for a week+, and then I have a speck of it in my food and am immediately sick). - I get very light headed easy. I have had my blood tested multiple times, everything is fine there. I just get light headed easily! On planes, during exercise, after sitting for too long... my doctors have assured me my blood work is great and I have never passed out from it so I'm really not even sure if this would be an issue. 36-48 hour fasts haven't made it worse, but I'm not sure if it's because they aren't super long or not. I guess I am just wondering if anyone has experience with food sensitivity after breaking a fast and if light headedness while fasting is hightened/common? I have been feeling great and find this type of fasting to be a breeze with huge benefits so I really would like to continue this and go longer if possible! Thanks everyone in advance. This group has been so informative and helpful to me and my experience!