Welcome to HW, I hope you like it here and we can give you some information to follow up on. I have tummy woes at the moment too..and have been put on an elimation diet (those mean doctors!! - no cheese?) I have not taken Lexipro but I believe that anti-deps have a good effect on the stomach problems; UC, Crohns, IBS etc. Especially the older ones termed "trycyclic antidepessant" are commonly used to ease pain from these symptoms.
Possibly the UC and the anxiety problems go hand in hand. I'm not a doctor so I may be wrong, but anxiety attacks our central nervous system and that may be partly the base of your problems. Do ask you doc if you have any concerns.
Welcome again to HW. Feel free to post about your anxiet and UC. We are a supportive community. Nice to meet you Megs