You said it yourself, you have settled down. And all too often, for a lot of couples, settling down means settling in. Settling in to routine. Settling in to expectations. Etc.
Try to liven things up with your boyfriend a little bit perhaps. Go on dates with him out to places you two have never been. Play games while out on the town (have him try pick up lines on you at a bar, for instance). As far as sex goes, maybe try a little role play. And if you have lesbian fantasies, I wouldn't be surprised if your boyfriend was cool with letting you try it, especially if he were there for it.
Don't worry too much about the other crushes and things. You boyfriend has probably had a few as well. Things we can't have always look better to us. But only in the short term.
Good luck.
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