Ah, you have an NRE situation. Well, NRE is quite a force of nature, it can blind your husband and make him neglect you without realizing it.
In a word, don't let him. Remind him, "Hey, I'm here too." He honestly doesn't mean to neglect you, he is just all "drunk with new love" right now. It is alright to give him reminders that you still need his love and affection too; he is going to have a tendency to forget.
Not to let him off the hook or suggest he isn't responsible for his behavior. I just know what it's like, having gone through the NRE process myself. There are things about the way I handled it back then that I am not proud of now. Your husband is likely to end up having a few sheepish regrets as well. And a new appreciation for the reminders that you give.
There is another thing besides NRE, it is called RRE (for Renewed Relationship Energy). It is a phenomenon where his excited feelings for his new partner spill over into his existing relationship with you. That's something that should be happening. If it doesn't happen, tell him, "Hey, I need some RRE!"
Hang in there. I think you will find that this all gets easier, a little at a time.
Love means never having to say, "Put down that meat cleaver!"