Is marrage what she really wants or not?

its not like im thinking about getting married, but ive been dating my girlfriend for 3 years now , and our relationship has become strange, i feel like the pion is leaving. I take her out on dates, i send her flowers, and i do a lot of romantic stuff but when it comes to I have to initiate it and its happening about once every 3 months, and every time i try she says she dosnt want the relationship to be about . I know that the will die down but once in 3 months. she's tried to have a break and also tried to break up with me, but being gullible i stay with her. yet every time im with her she talks about how were going to get married and everything, im not sure what to make of this, any ideas?