I agree with above. to me, he sounds 'stuck'. He's trying to make some money that you and he could really use. It's hard to be away, I'm sure. Especially while pregnant. But he hasn't dumped you or left you but instead is taking care of some financial needs. When he returns, I'd sit down and talk about long term plans. If you two need to move so he has better chances at work, then that might be a good option to have him at home more.
my husband travels for work and will be gone over 2 weeks at times depending on the trip. But I see it as what he has to do to be our provider. It's hard when the kids are little but then you get used to it.
I am thinking part of the problem is not being able to contact HIM when you want to and not knowing the details of when he is returning. That is unfortunate. Perhaps a prepaid cell phone for these trips would be wise to save up for so you can still feel like you are in contact.
That not being able to reach him or knowing when he is coming back would really be hard, I'm sure. That part I would definitely work on if he is going to be out of town like this.
The good news is that he sounds like he cares very much about you and would rather be with you than gone. That part is good. peace and good luck with the baby
He is staying in contact with you so that's a good sign. If he's getting in more work time that's a good thing too since you have a baby on the way. Try not to stress. Hopefully he'll be home soon.