Giving up

I'm done!!! Idk what I'm doing wrong but I try everything for my wife. I try romance,massaging her,write letters, I decorate with flowers around the bed room, I try soon much and nothing. We haven't had sex for three weeks and l been putting in my all to her and I feel like I'm waisting my time. I work 7 days a week and I give my lil time for her and nothing... Idk if I'm wrong but tired very hard to do everything for her to make easy for half and she doesn't even care its been like this for 3 yrs ...so please help me and tell me what I should do or try