What Causes Vaginal Bleeding While Using Clitoral Stimulation To Masturbate?

hi i am 21 years old and i have been using clitoral stimulation to masturbate for a few years now but the last couple years it has caused me to start to have vagial bleeding, very much looks like the start of a cycle. This used to just happen once in a while usually before my cycle but now its almost every time. I am on seasonal and diclofenac. wondering if it is possible it is just leftover from my cycle being as I do not have one every month or if it is something i should worry about?