Let me just throw in here, that in my experience as a professional student 'getting a girlfriend' does NOT reduce stress. I'm not saying you shouldn't do it, just that having that expectation might be unreasonable.
As far as how I date... generally I've had the best luck meeting compatible people through OKCupid. Joining local poly-friendly interest groups is also a good way, but I find my time is a little limited for attending events.
When you write your profile, or contact people you'd like to date, make a mention of your relationship style early on. A lot of people won't be interested, but in my opinion it's better to figure that out right away than spend the time and heartache on people who won't accept it. You don't have to (and I don't recommend) laying your whole story out on the table immediately, but do say something to the effect of 'I'm already in a relationship and she knows I'm dating other people too.' Answer questions as they ask them or you feel the desire to share more info.
Good luck to you, Blessed Be.
"Owning your feelings is basic to understanding the boundaries of where you end and the next person begins and the perfect first step toward self-acceptance and self-love." The Ethical Slut pg 69, Dossie Easton and Janet W Hardy
Scarlet's Blog: http://scarletsredletters.blogspot.com/