What Causes Slight Vaginal Bleeding With Light And Short Periods?

lately in the morning i feel like almost like i have a UTI but it doesnt burn and im always slightly bleeding. this feeling and bleeding last no more than an hour and not ever day but most days. i got my tubes tied 5 years ago and have had very regular 7 day periods ever since. my last two have been very light and only last 3 days. any suggestions on what is going on?