What, specifically, bothers you about him seeing someone new? How long have you been with your guy? Are you jealous? Is he all twitterpated and paying her too much attention? Is he seeing you less? Is he spending YOUR dates texting her? It's boundaries time. What would help you to feel more secure?
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
There's no lying in polyamory!
I'm a 58 year old woman with 2 partners:
miss pixi, my live-in gf, 36 (together since Jan '09)
Ginger, bf, 61, married, lives nearby (together since Jan '12)