Do guys get complacent in relationships??

I have been dating this guy for 5 months now. He is really sweet and we get along well. He is always telling me he doesn't know what he would do without me, and how much he loves me. He used to always tell me how beautiful I was. He doesn't anymore and I don't know if it is because we have been dating a while or what. This is my first really serious relationship, and I guess I miss the spark that was there in the beginning. He says some nice things, but it is the same things over and over. what can I do about this?
Do guys get complacent in relationships??
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