Am I being unreasonable to get upset over my boyfriend's ex?

Okay, so a bit of brief background: I'm 19 and have been in a secret relationship with my ex English tutor for about 7 months and there's a fair age difference. His ex girlfriend was also an ex student - older than me, she was about 22when they began a relationship. Well ever since I found out his ex was also an ex student, I've found it incredibly hard to deal with. Whenever I've told him that I find it hard and that it fuels my insecurity in the relationship, he just tells me to grow up and that he has bigger problems to deal with; money, work etc. In his house, there's still a lot of traces of her: cosmetics in bathroom, photos, shoes in porch, things in bedroom. I really don't mean to be so demanding and selfish to expect to see no traces but the fact that she was also an ex student makes it very hard - if it was genuinely just any other ex, I don't think I'd have the same problem. There's also still contact - she'll ring or text him and he text her on her birthday the other week. They've been out of the relationship for 9 months (both in new ones) but I just find it so hard to deal with..I hate the fact that I can still feel her presence and that there's still need for contact. Am I being unreasonable or is he being insensitive?

Put the internet to work for you. via Personal Recipe 2629979