Is my boyfriend using me?

We have been dating for 5 months and lately I feel like he’s not taking the relationship as seriously as I thought. He refused to come to spend Christmas with my family and new years too and he made up a lame excuse that he had to work. And he almost skipped exchanging Christmas gifts with me and almost didn’t come over my house to exchange gifts. And he cancelled my date twice when he promised he wouldn’t. And he usually sexts me when he is horny then is quiet on me when he’s isn’t. Why is he beginning to act this way. All I want in life is to marry one day and have a family. Is this my fault? Why is he acting this way and what should I do about this?