Feeling Like I'm Missing Something

It's been three years since my partner and I got together. We have a great life, stable jobs, but lately, I've felt this strange longing in bed. Nothing major or specific, just that it doesn't feel... complete anymore. Maybe I should be happy with what we have, but there are these moments when I wonder if I'm missing out on something, you know? We've talked about it before, and he's supportive, but sometimes I think we're both a bit too comfortable now. Does this make me a bad person for having these thoughts? Or is it okay to just want more excitement in our sex life? Anyone else feel this way?