I had the urge to use the restroom frequently as a side effect for a while, but it went away after a while. I can't remember how long that issue lasted. I think it might have been because I was drinking a little more than I was before.

You can buy test strips off the shelf at your local drug store(Walgreens, cvs, etc.) to test for a UTI. It's like $9 for a box with 3 test strips. I know you said you ruled a UTI out, but if you want to check again in a week or so but don't want to go to the doctor, that's a quick and cheap way to check without having to go in.

I haven't had any weight change with lamictal. The drug is generally considered weight neutral.