last week my boyfriend invited one of his ex-girlfriends so we could have a 3some. i was open to the idea at the time, until i found out why she was his ex-girlfriend. i was laying on the bed playing with his cock, when she put on a blue strapon and then rammed it, lube-free, into my ass. i was so surprised i went crazy on his cock and he creamed my mouth, but it was so painful. he loved it, and thought it was a real turn on whilst she was fucking my ass. now he wants her over again in a couple of weeks because he liked it so much, but i dont want her doing that to me again? what to do?