The main time Ginko and I see other people is when the other is at work, that way it doesn't cut into the time we have together so much. I'd be more apt to be bothered if she were seeing someone in the limited time we could be with each other. I guess it's different for everyone. It does get a bit easier over time, provided you both have good results in seeing other people and you respect each other's boundaries whatever they may be.
It's fine to have no sexual interest in your bf's other partners. What might need to be looked at is the double standard of him expecting you to only have one night stands with the opposite gender while he can build separate relationships.