You might have your husband research into the causes, solutions, and especially the aggravating factors for problems of this type–because it is not just one single problem that causes this. Also, be aware that psychological causes are real causes, because most of the things that your central nervous system does to the rest of your body are not under your direct control. You can’t just “tough it out”, because when your body hears “tough it out”, that can have pretty much the opposite effect of when it hears “you are safe, you can relax entirely”.
Do you see where I’m going with this? In addition to whatever is physically causing this, you have to be aware that normal sexual functioning presumes a physical situation where the parties are relaxed and free to simply do what seems to be the thing to do, with all anxiety-producing things a million miles away. If the part of your body, your brain, that is responsible for letting the rest of your body know there is a danger turns on the “be wary” sign, then that can cause problems. When anxiety-producing factors intrude, nature lets us know that the trip beyond worries will have to wait for another day.
When it comes to thoughts, your body usually responds as if all thoughts were positive commands. Tell yourself “don’t think of an elephant”, and somehow all your body gets is “be wary of elephants”. You certainly can’t get pictures of pachyderms out of your head! Don’t want to think of elephants? You have to give yourself a mutually-exclusive positive command, instead, like “think of predators” or better yet, “think of birds in flight, floating and light, free and floating on the wind, forever and ever”. It isn’t very likely that you’re going to see Dumbo floating by, but if you do, he’s light and free, so what of it? You’re not going to be worried he’ll step on you.
So part of your “homework” is going to be to maintain a feeling in you that you are safe and that ultimately everything is right with the world when you’re intimate with your husband, no matter what else happens. Easier said than done, perhaps, but that is your (plural) goal, whatever other goals you have.