Does fitting in have to mean conforming?

If you're conforming against your wishes then you're not fitting in. Fitting in means making your personality a part of your working environment, not allowing it to disappear under a culture of which you can't be a part. If the culture of your workplace doesn't appeal to you, then it's worth trying to develop alternatives. If, for example, your colleagues get legless in the pub every evening and that's not your thing, try suggesting alternatives - a sporting outing, perhaps, a musical gig or a movie. The odds are that you'll soon find like-minded people who'll welcome the chance to do something different. Of course, it is possible that, despite your efforts, the culture is simply one you could never fit into. But most workplaces contain a remarkable variety of people, and trying to make connections is nearly always well worth the effort.