Is it normal the way i feel....

This is about the wonderful relation i share with the guy who is no less than the prince of my life. Its been 2 years that i am in a relationship with him. He is a genuine guy and we love each-other to the most we can. Our relationship sees all kinds of ups and downs like anybody else'. Inspite of all this what always matter is the better things to see and feel great about, the bond we share and the happiness our togetherness gives us.
We both have had our pasts and this is a second relation for both of us. But we both claim that it only was for good that we moved on in our past, cos there is nothing comparable to the beauty of our present with it. But there is a thing that glitches me most of the times, whenever we have an argument. HE BRINGS HIS X IN IT ANYTIME WE FIGHT. He talks about her being special to him still for all the past first moments he has shared with her. His first kiss, his first ever intimate moments. And it hurts me to an extent that it only ends up in getting things more screwed. He loves me a lot, i don't doubt it. And cos i love him, i feel it is normal for me to feel hurt for the times he talks about her in this way. And i believe that if i hold a strong position in his life he shouldn't bring her in between us and spoil it. And when i argue over this to him, he calls it immaturity and excessive nagging. He thinks I haven't accepted him with his past still. And my point of concern is, that she has been a past, so it should not affect the beautiful present we have, and if it hurts me, he should understand it and not bring her into our discussions. I never discuss my x wid him for the similar reasons, cos i know he feels bad with it. It is not that we never talk about her, we do at times when there comes about sharing a generic situation wherein she was a part of it, but whenever he talks about his and her intimacy i am highly hurt.And he every-time so strongly claim me to be immature to stick to such stories from his side and fight over them. I really want to elicit a general opinion of people and know if their present suffer cos of their past relationships.. And if it is normal to feel hurt in talking about her as a part of him till today. All i know is that i love him immensely and intensely.. and i want to be the only special person in his life. first moments in anybody's life will be special but shouldn't discussions about them be avoided when it hurts your partner whom you really claim to love a lot... ????