If you inserted the end of a hairbrush into your vagina, that is likely what caused the bleeding. Please don't put any object into your vagina that isn't designed to go in there. In addition to hurting yourself, you run the risk of bacterial infection.
If your lower stomach hurts, it might be that your period is about to start, and you are getting menstrual cramps. If the pain worsens or doesn't go away (and you don't get your period), you should definitely talk to your mom and see a doctor.
This even is unlikely to have affected your future fertility. But, as I mentioned, please don't insert anything into your vagina that isn't designed to be there. You could seriously injure yourself or get an infection.