Speaking as a husband, I can tell you that your husband would probably rather you asked him for the moon. It's a massive, monumental, impossible undertaking, but at heart all it is is one big logistics concern. Whether the moon is made of rock or cheese, it's a physical object and your husband has lots of ideas on how to move it, or at least pieces of it.
A woman's feelings, however. How to make a woman feel wanted, desired, and important? We have our best sages working on that one 24/7. Sometimes they emerge from their sage-cave and ask "Have you tried giving her chocolate? We heard they like chocolate"
I'm going to assume that your husband is like me, and has no intention of replacing his first wife in his affections or moving her out, and I really think that you should assume that about your husband as well. I think it has a good chance of being the objective truth, and (more to the point) it will help you with your feelings.
I'm gonna ramble here for a bit, but I'd like you to follow me here. I was once told that some people... somewhere... who wanted to capture and tame wild horses would briefly lasso a wild horse, and then tie an already domesticated donkey to the horse and let them both free. The horse, having superior strength would then drag the donkey over hill and dale, far away. But the donkey, wanting to go back home where the oats are kept, will always be pulling the horse toward home. The horse is resistant, and any time that it insists, it drags the donkey wherever it pleases... but the donkey has but one destination and eventually the horse finds it easier to travel with the donkey than against the donkey. Some weeks after letting them both loose, the donkey and the horse arrive at the corral. The donkey is happy to be home and the horse is conditioned to do whatever the donkey is doing, so taming the horse becomes very easy from there.
In this analogy I'm using, the wild horse is your feelings: They are strong and difficult to control and you just can't simply MAKE them do anything they don't want to do.
The donkey is your thoughts, what you think about and what you tell yourself.
My suggestion is that you discuss your feelings somewhat with your hubby and ask him whether he wants you and desires you and whether you are important to him or not.Then rather than asking him to make you feel important and wanted and desired (which is sometimes so simple it can be done offhandedly and at other times nothing seems to work), I would suggest you would ask him what you should think, and what you should tell yourself when your feelings start to run away with you.
For one, you will not cause your husband feelings of despair and helplessness in the face of your feelings. A temptation for men when facing a problem as difficult and illogical as a woman's feelings is to ignore the problem or in some way lash out against them, which I don't think will help your emotions either.
For two, even if your husband succeeds brilliantly at making you feel loved and prized, that doesn't mean that your feelings won't jump you as soon as he walks out the door next time he's out on a date.
And third: Just like we are all responsible for our own thoughts, we are all responsible for our own feelings. Ultimately, your husband can only do so much in assuring you, even if he does exactly what you ask him to.
Hopefully my wife, Rainy, will forgive me for sharing this, but I feel it is pertinent. Some time ago she was feeling down and insecure and almost nothing I could say would reassure her that I loved her like birds love pooping on my car. With all the devotion and glee that they put into it, that's how much I love her. But she just didn't feel it was true. And I would ask her "What can I do to make you feel better?" and she would reply "Just lay here and hug me for awhile"
And so I would, and she felt better. For as long as I has hugging her, things were not so bad for her. And I would sometimes hug her for 3 hours at a time! But the moment I let go, because children need to be fed and showers needed to be had, the feelings would come crashing down on her again. So not only does your husband have a limited ability to change your feelings at will, any change he can effect will (probably) be only a temporary fix.
But if you yourself are able to control your emotions by repeatedly telling them what is true, and not giving in to anxiety, then you will have done yourself and your husband and your husband's other wife a valuable service indeed. Your worth is far more than rubies, and chances are your husband knows this already, and you will prove it again and again until your husband's heart swells with praise for you.
uh. Says me anyways...