Why is my boyfriend cheating on me but denies it no matter how much evidence I have, why is he with me if he's unhappy?

How do I make him settle down with me? He loves me but always complains that he doesn’t have money to marry me. What do I do?
Partner can go days without saying "I love you" to me. It makes me feel odd to go days without hearing it and/or having to initiate it majority of the time. What could this mean & what should I do?