Here are a few non-alarming causes: *Do you brush your teeth often enough? If you brush your teeth maybe once every two or three days then bleeding gums would be possible because they wouldn't be used to the rubbing from the tooth brush. *Do you brush your teeth too much? Brushing your teeth too often may possibly cause gums to wear down and become damaged, but I'm talking excessive, over 3 times a day. *How old is your toothbrush? Are the bristles okay? When was the last time you changed your toothbrush? Sometimes after a while, bristles on the toothbrush may spread out to the sides, or maybe there's that one annoying bristle that sticks out more than the others? I've been brushing my teeth before and has a bristle that was a tad askew poke my gum and cause it to bleed. *Are the bristles firm and stiff or really soft? Sometimes leftover toothpaste in the brush can make the bristles stiff and sometimes stiff bristles may be a bit harsh on gums. Try going for a more soft bristled brush if you feel comfortable with that and see if it helps. *Are you a woman and pregnant? This one seems highly unlikely since it's been happening on and off for a while, but sometimes pregnant women have problems with bleeding gums due to the hormone shift. More alarming reasons could be the result of a gum disease. If you are seriously concerned then please see a dentist, or if you are seeing a dentist for regular check-ups, mention it next time you go.