Maybe ask tell him you're feeling a bit insecure and ask what he likes about you. I think him constantly talking about his ex is because he misses her? and that is downgrading and horrible on you. I know a friend who went through this. And stop trying to complete! you are not her! you will never be like her! he dumped HER not you. so that means he wants YOU. So you much have better or different qualities! Block her facebook profile as if you keep looking it will drag you down further, you need to wear the things you want and your confidence will improve!
It sounds like you bf is missing her and is obsessed (bit strong a word) and by him talking about her after taking your virginity is not on! thats horrible! Im sorry, but I am really not impressed by him already! it sounds like her hadnt moved on when he got with you :/. I think you may need to come clean and tell him how its making you feel (only say as much as you feel comfortable) I find it is much better when I confess to mine when I see someone who I think looks better and she'll give me reassurance and then i'll think, she's with me so I must be doing something right. If he is still talking about her after 3 years im sorry to say this but he isnt worth it and you deserve better as no woman should be in the shadow of an ex! it is unfair dating you if he is not over his ex!