It's a bit funny that you've only had one reply to this. Maybe they feel like I do, like they don't know how to overcome envy. Envy is hard. You're asking how you can stop yourself wishing it was you that was walking on the beach with your girlfriend, when you are however many miles away. You know what? In your situation, I'd feel the same way. Envy would be a problem if you were living together 24/7, 365 days a year and every time she went out, you wished it was you. But, man, you're in a totally different country FFS. Of course you going to feel how you feel. I'm not sure why your girlfriend doesn't understand that. I guess if she's got a husband and still has your child and she's seeing other people, she can't relate to what it's like for you. What you're trying to say is that it's not just that you can't see her, you miss your baby, miss your life in America, and for 3 months, it just vanishes. That's really tough and I feel for you. I'd be having a nervous breakdown if I had to live like that and deal with poly on top of it.
The only thing I've ever read about dealing with envy is to think of the happiness the person you loves is getting from having that thing. I don't know if that works, because surely you'd be even more envious, knowing how happy someone else is. I'm not even sure what you're feeling is envy. It seems more to me like nostalgia or memories. Or the simple fact that you want to be with your girlfriend. Who can blame you for that? I'm a bit worried about what you said about her going on a date with someone you don't like. Why did she go on it if you dont like him? Especially because you haven't even been back for three weeks yet. Surely these things take time and to be honest she surely could make it easier on you by waiting a bit longer. Or maybe changing something. Or even just not telling you what they did on her date. I don't understand why she would expect you to be ok when not only are you away from her and your child, but she went on a date AND went on the date with someone you don't like AND told you about what they did.
The only thing I can really think of to say is that I have sympathy for your situation. I think maybe you can ask her to keep the details to herself a bit from now on. When big things happen in life, like losing our house, starting a new job, losing a person, etc. it's like our stability is gone. You don't have a career, you say, in your home country, so you have to do rubbish jobs. That can't be fun. You don't have her, or your child, or your business... so... duh.... of course you're going to feel shaky for a bit. We all become poly by agreement and I don't think there's anything wrong with having open long distance relationships. But both people have to admit that it's going to make things worse sometimes. You shouldn't be scolded for that. She should be giving you praise, saying thanks so much for getting through me having a date with this guy you don't like when you're working a shitty job just so that you can come to see me and when you're upset because many of the things you love in life are here with me. Maybe she should try being in your shoes and see how easy it is to look on the bright side. Its nice that you want to overcome it and I hope you do. But seriously she needs to give you some more patience and love right now. Take care sparklepop.