Tearing during doggy?

So I've been seeing this guy, no strings attached (I'm 18, he's 22) and he always tells me that he wants to take me from behind and I want him to too. But every time he does he like rips my vagina on the back side and it hurts so much so I make him stop. And then when we keep going in a different position,he stops and freaks out because he made me bleed and tells me that I should "get that checked out" so neither of us get off and I just go home. Then he expects me to come over the next day despite my bleeding, torn vagina. Does anyone else experience tearing during doggy style and does anyone know a way I could situate my body to avoid it??? Because I really enjoy the way it feels when it doesn't hurt me and I know he really likes it too...