UTI vs. pregnancy discomfort?

I'm oddly susceptible to UTIs as it is, but unfortunately I don't show many of the normal symptoms. Maybe a little backache or nausea, but usually nothing else unless it makes it to my kidneys. No fever, burning, constantly having to pee, anything. Makes it really hard to know when I'm coming down with one, especially when nausea and backaches are a normal part of life lately. But I've been feeling a lot of pressure/discomfort around my bladder for the last couple of days though, and I'm trying to decide if it's just normal pregnancy discomfort or a bladder infection. I'm going to call my doctor tomorrow, but have any of you ladies experienced this? How did you know the difference?