What should one do if ones wife can on longer attend to ones needs?

salaams , my wife and I have been married for 12yrs , we have 3 young children , the youngest just 2months , our personal relationship is beginning to suffer a lot ( it is that we can never find time for ourselves ) . I try to initiate sex with her most of the time she is either too tired or when it happens I feel that I have used her , I get this feeling from the way she reacts . I have spoken to her about this issue . She says that she will try to be more accommodating to my needs , but nothing happens , I have told her that she is forcing my patience and that on numerous occasions I have cursed her for not attending to my needs.
I don’t know what to do anymore , I have at times considered finding another woman to fulfill my desires
But then the moral thoughts take over and I reconsider what I am thinking of doing.
This is putting such a strain on me , I don’t know how to cope anymore