Loosing the spark

I feel that my partner has gotten bored with me. The beginning of the relationship was flooded with romance and passion. For the last year I feel as we've lost the fire. Of course having my own insecurities makes me feel like it's about my appearance. I have let myself go a little. I put on a little weight and don't spend half as much time getting ready as I used too. He says it's nothing like that. He's just "used to the relationship". I don't know what to do.