It is possible to have a UTI without any symptoms at all. I went into early labour at 33 weeks with DS due to a UTI that was unsymptomatic. It has little to due with hygiene, just being pregnant can make you more likely to get one. Ethical nutrients do a Urinary Tract Support supplement that is great, drinking cranberry juice too is a good way of keeping urinary problems at bay. You might not have a UTI but you could have some irritation in the bladder, drinking lots and lots of water is also god.

Also remember that as baby grows he will out more and more pressure on your bladder and it can get very painful at times. If in doubt though check it out with your midwife or care provider.