Ay mama, I totally get the worry kasi ang dami ng factors when you're TTC! So from what I know, UTI mismo at ang antibiotics prescribed by your doctor ay normally okay lang for conception, ang doc wouldn't give something na harmful pag trying ka talaga. Pero honestly, the short period and negative PT might be stress-related or just your body doing its thing, kaya better talaga to follow up with your OB about the whole situation together, whether it's the infection, the short cycle, o ano talaga ang nangyari, para may peace of mind ka. A few of my mum friends din nag-panic with weird cycles while TTC, but once na-address ng doctor ang root cause, sobrang normal na ulit ang nangyari. Rooting for you, mama!