Is it ok that my boyfriend's ex girlfriend bothers me? And should it? Long but need advice! Plz!?

So my before my boyfriend and i got together we were good friends. He would always tell me about his girlfriend at the time. He told me everything: how she always needed to know where he was, how she constantly called him and could never go 3 mins without calling him back. They had a very rocky relationship, didnt go so well. Anyways, when we went out they had been broken up for at least 3-4 months. Again he would always tell me about her, the crazy annoying things she did. We have now been dating for 8 months and she has called him at least a dozen or more times. Once while we were on our first date (which i brushed off and didnt strike me as odd now but it bothers me now), she has texted him countless times, and has even called me at one point all on other peoples phones and restricted lines which we have all ignored. ( when she called me it said restricted so i picked up. i knew it was her that called me from the voice, she asked me my name and i said it and she hung up). She still continuously calls and texts. My boyfriend tries to justify her actions i suppose by saying its not as much as before, but its still one to many. We ignore her everytime but she still manages to try to call or text. I have not let it get to me for 8 months till now. It all just seems too much. By boyfriend said we shouldnt let her get to our relationship and she really hasnt in my oppinion b/c we still love eachother very much and plan on a future together. He has also agreed to change his number. We have blocked her from facebook and everything and still she manages to get ahold of us. It bothers me to the point of crying and when it gets to me all my boyfriend can say is well it looks let we let her win. Thanks alot. (obviously im upset with my boyfriend for that comment but thats not the point.) Story aside what i really want to know is, 1. Is it normal that this bothers me so much? 2. Why? and 3. How can i make it not? Please help. It would put my mind at so much ease. I would hate to think that im letting this jepardize our relationship.