My boyfriend's crazy ex is trying to ruin our relationship

Me and my boyfriend haven't been together very long, actually we've only been together for about 6 months. Him and his ex was together for a year before me and him and he stated several times how she made him feel depressed, she wouldn't let him have any time to himself, was very controlling etc. But she also took his virginity. She won't leave him alone, on her social media page, her profile picture is an old picture of them... She changed her last name to his name, and she even went as far as to text me. So I answered, and we got into a little argument, she started sending me pictures of them two, like sexual pictures.. It was awful. I blocked her, but she kept rubbing it in my face that they both lost their virgintity to each other. Now I can't stop picturing them together and we haven't even had sex yet, so she was literally his first and his last. Which kills me inside. Now she's literally stalking our relationship, and it really irks me. I know he loves me, an I know she's crazy. But I can't seem to get rid of the bitch!