“It pisses me off anytime my boyfriend speaks about his ex”

"It pisses me off anytime my boyfriend speaks about his ex"

From a female blog reader:

 Pls do not show my identity. I am a 25 year old girl n I have being in a relationship with a guy close to 3yrs now, we truely love each other, he shares all his family problems with me, even what happens in his office, his monthly income, his savings and he is very supportive financially. Infact I know virtually every plan he makes in life n he always stands by me even dou his family are against our relationship he still wants to marry me. But d problem I have with him is this: he tends to talk about his ex gf each n everyday, n that is pissing me off, even dou he only says negative things about her, there is no day that will pass without him talking about her either 1 way or d other. Each time I tried talking to him about it. He will say “I am only telling u so u wont make same mistakes she made” I love u n will never go back to her”. Then I will become soft. But d last time we had an argument he told me she is even better than me but he later apologised that he said that out of anger then I forgave him. My boyfriend is very hot tempered I dont want to do anything that will make him angry or spoil our relationship but hearing him talked about his ex gf keeps killing me daily. What do I do to erase her memory completely from his head cos I am loosing patience n focused.
Note: He loves me alot n I love him too. We are planning to get married