Hi. Welcome to the forum.
Other issues to consider are the ramifications of a workplace romance, which can be a can of worms even when multiple partners are not involved. A few of the many questions to consider:
Is there a company policy in place? If there is, I betcha polyamory isn't covered in it. This means you'll be in uncharted territory with your HR dept. Are you prepared to deal with that?
Are you prepared to be an ongoing topic of gossip and innuendo? Because you will be.
What if things go badly? He'll still be your co-worker, and you'll still see each other there. Will you be able to deal with that? Will he? Will your bf?
Consider carefully before you move forward. Workplace romance can fraught with peril. Proceed with caution. Good luck to you, whatever you decide.