The same thing happened with me and pudsey but the other way round. In that i mean a male friend of mone joined us. Infact i had no idea what was happening until it actually happened. I think it is is better to have the third person involved be someone that you both know and trust cause im our experience in makes a great deal of difference rarther than just going and picking someone off a website that u havent even met before.
Threesomes can be fantastic belive me ! thats only if your 100% sure though and to begin with i wasnt but then i relaxed and really enjoyed it. And it was one of the best things that has ever happened to me sexually.