What is going on with him? How can i get over friends weird behavior?

i've known him for 4 years. he's married. we were all on good terms. then this new lady friend came into our circle of friends. she always cook for this couple. so they became very close. he gave her a lot of attention. his wife likes her personality. she wanted to be my friend. i allowed that for abt a year. then i just got tired of her. anyway, throughout the time i knew this couple, the wife has been good to me, but he has treated me like i don't exist. on and off, he seems ok with me but quiet when i am around. then other times, just seems angry with me. funny thing is, we dont ociate on a personal basis. he is only comfortable around our other frineds, his wife, and this new friend. anyway, recently for the past 2 weeks, i seem to be in his company a lot. he seems nice and talkative. then suddenly, he is back to his cold ways. the last time i saw him, he had a party for our friends and i was one of those invited. anyway, needless t say, he asked his female frined and 2 others to cater food for the party. but i noticed that during the time people were eating he was walking around near to her and likewise her. then at few times, he was standing in a corner looking at me acroos from where i was sitting. then, for the other times, is was tlaking out loud with others and interacting with this friend. the funny thing is, to me they seem flirtacious even when the wife is right there. but she doe snot seem to mind how close they seem (to me). but lately, the wife has been giving me the some cold sarcastic tones. so i am i a little taken-aback. anyway, i lost my appetite and did not eat any of the food. i just pretended to be happy there. he was ok and talkative with me the last few days, which i thought was strange, then at this party, he was in his ego mode. he and his wife will be leaving town for a month. so i dont know if its because he is leaving. anyway, like i said, he and his wife are close now with this newer friend. and when i am around he is withdrawn and quiet.