Hi snowh8er,
I'm really sorry to hear that you're going through this. It sounds to me (at least from what you have written) that you're not so much threatened by your husband's new girlfriend, but either envious of the NRE between them, or more likely plain *despondent*. I think that, in poly, we are quick to attribute every negative feeling to some form of jealousy when, sometimes, it's not jealousy - just plain sadness. Why wouldn't you be sad to see your husband doing things with his new girlfriend that he's never done for/with you? Why wouldn't you be sad to see that your husband is capable of wining and dining... just not with you? Sometimes it just plain sucks to be in the role of Old Faithful, watching a partner go gaga for someone else. Sometimes that isn't to do with insecurity, and sometimes it is.
You say that you are left home taking care of your child while your husband is off texting, dating, and planning weekends away with his new flame. Do you and your husband ever take weekends away together or go on regular dates? Or has all of that stopped? Have you talked to him about how you feel? If you guys don't 'date' each other any more, have a hard think and try to figure out what part you might have played in that? Do you try to initiate dates, texts, and weekends away, or do you leave it to him? What happens if you do try to initiate?
I tend to take two viewpoints on this kind of thing. On one hand, I try to remember that new love/lust is different to long-term, stable love. I try to allow some room for NRE, and try to understand when my partner is going loopy over someone else. I've been poly for 4 years, and I've only recently reached the point where I can actually smile about this if my partner is into someone brand new. Part of me feels that relationships will take whatever shape they take, and they cannot be forced.
On the other hand, I believe that existing relationships die if the effort is not put in. If life becomes all about child-rearing, home-making, shopping, laundry, watching tv, etc., it can lose its zing, no matter how wonderful this type of cosy intimacy is in its own right.
I've also found that we don't all agree on what makes a happy relationship, or what we desire from each relationship. For instance, some people are genuinely quite happy to have a comfortable life with a long-term partner they love, without worrying about the loss of NRE. My girlfriend, for example, will often say that she's considers all time with me quality time, even if we're grocery shopping or just watching TV. She'll say that if we're going through a sex drought, it doesn't stress her out, because she appreciates the intimacy between us, like cuddling, massage, etc. For me, it's not enough - I need adventure and change in a long-term relationship. I need actual dates, loving texts, and a great sex life. It doesn't mean that I don't appreciate the cosy love stuff - it just means that I need more than that. What do you need, and what does your husband need? If you haven't already, why not speak to your husband and discover whether he's been happy with where you guys are at, or whether he wants to inject some life back into your marriage as much as you do?