I would! go easier. I can relate though. I am a guy but I recall when I first started masturbating I used to do it so much my penis might get a little sore or even bleed a tad.
But are you sure the blood is from the masturbating and not, say, your period? The reason I say this is that sometimes with my girlfriends if they hadn't had sex in a while the first time we had sex if I had sex with them really hard and long all of a sudden their periods would start. They would all be like - whoa! my period is not due right now at all!
So, really intense sex can BRING ON a girl's period. So if you are really having a good time maybe it is throwing your body into your period.
Also, you know you can get lubricants for female masturbating. Look at whole foods type stores like natural grocery stores. Water based (not petroleum jelly) lubricants for females. Then you could masturbate away and probably not injure yourself. Would feel better too.
Podee, what you are describing is not 'bringing on' a period. The menstrual cycle is very set and the period only starts naturally when certain chemical/hormonal things take place. Having vigorous sex will not do that. All that does is 'injure' the uterus enough to bleed. It is not normal.
Seriously, I am not talking about injuring the vagina leading to bleeding. I am talking about women whose period is brought on due to vigorous sex. This happens and I know it for a fact.
Menstruation is hormonal in nature, and sex and emotions all tie into this. I have had girlfriends all the time who started their period after being sexually active with me and told me that they were not due at all. The amount of blood and the nature of the blood is not consistent with injury but simply with the coming on of a period.