All women are different and start showing at different times.
Have you seen your Dr about the UTI's you're having? To help with them you should drink plenty of water, use the bathroom as soon as you feel the need and urinate before and after sex.
I hear that for most ppl it's around 18 weeks for sure. i'm 14 weeks and 4 days an feel fuller already and am starting to out grow my clothes. but to strangers they pry couldnt tell i'm pregnant. it does feel like its gettibg bigger faster at this poiny though. and my ob told me that cranberry juice helps and it really does. drink as much of it as you can until you absolutely have to pee. then do the same with water right after. it helps flush it out right away. I did it an it fly worked. you may have to do it a few times a day. if it doesn't work with in a few days tell your doctor.