I wouldn't think a hair brush is the best thing to masturbate with. Things like that are easy to hurt ourselves with. However, I don't think that has anything to do with not having your period. If you are young, this is actually quite common to be irregular. Things that make us late are stress, illness, changes in routine, weight gain or loss, etc. Thyroid can be involved. Depending on your age or history, you should talk to your parent about it or see your doctor. You can leave the masturbation part out as again, that's not a factor. But the brush can cut you and hurt you so don't use it anymore.
Is this the first time you have had irregular timing with the periods or is that not unusual? Because even if you had cut yourself (and probably you didn't unless you were using the scratchy end of the brush) it would have healed by now. The fact that your period has been gone for three months is probably unrelated to the masturbation.