First of all-You seem to have all these complaints about how she dresses and flat out said that you think she's only faithful because you think she would annoy another guy. This is all probably transparent to her. We are more perceptive than you think so when our guy has a problem with us-we know it. Maybe you should remind her of why you love her if you want to get her going again. Romance her, draw a bath for her with some candles. Intimacy isn't always about sex.
I'am a man and sex is just what i want been with my girlfreind for 17 years and the only thing that has changed his her she has no friends and does not go out she dresses not like lady at all and she has no sex drive it has become a job for her and no matter what i do it is always the same thing a job this has become a problem to me and i have been faithful all this time and all I want is too be sexually and mentaly in love with her but all this is to much for her to handle she is 100% faithful to me i know for a fact because there are no men in there right mind who can talk to her for more than 5 min. with out the man thinking she has something worng with her comunications with others and that is why I know she is faithfull plus i have been with her since she was 13 and i was 17 so what do you girls think is the problem i would love advice?
Another thing that can lower your interest is the behavior of the guy. Does he try to make you excited and ready? Does he talk to you about things and act interested in your life, or is he there apparently just to hop in the sack? You might want to re-think this boyfriend if he isn't apparently as interested in who you are as much as he is in your body. There are lots of sweet men out there who like women and are interested in having a real relationship, not just physical.
I agree with the other posters.. are you on any new meds at all? Lots of things can lower your desire for sex - BCP, any med for depression or anxiety, depression itself, etc etc...
Have you had your tubes tied. That happened to me in 2004 when I got my tubes tied.
Have you recently began taking a birth control pill? A common complaint is that knocks your libido down -
Best wishes.