I am a single mother 3. Divorced from the father of my two oldest and never married to the father of my newest 7 month old baby (and we are no longer together).
Divorce is extremely hard. That is something that you will have to think about long and hard. Only you can make that decision. I don't regret divorcing my ex, but it was very hard for me to reorganize my life to being a single parent. He was no longer there to help transport the children, deal with automotive things, and things like that.
Legal fees can cost you too and will only heighten the animosity you and your husband may have.
Like I said, YOU are the one who needs to make that decision. I would feel it out and try different things to get your husband to pay attention to you. You may being emotional/sensitive due to hormones from the pregnancy.
My steadfast saying though, "You might as well be physically alone if you are already emotionally alone." Meaning, if he's not paying attention to you, then you are already alone, just make it to where it's physcially alone too.
I suggest you seek some counseling. Good luck. And if you ever want to just chat, feel free to contact me. I've been through it all...