Uti during early pregnancy

Hey ladies! On Saturday I started to feel like I had a uti (discomfort, constant feeling like I need to pee after I just peed, and lower back pain) and I took at at home uti test and it came back positive and so I called doctor who prescribed macrobid.

I’m curious how long after taking the antibiotic should I start to feel better? I started taking it yesterday around 2pm, so I’ve only been on it one full day, but don’t feel a difference yet.