Breaking point!!!

I feel like I completely alone during this pregnancy. My other half is always gone due to work. He tells me one day that he will be home in three or four days and then it comes to the day he is suppose to be home. Then everything get changed and he doesn't know when he is going to be home... He doesn't even make that good of money. Like 1400 a week... I just can't stand that he won't be at the doctors office with me. He won't be here with me threw at of the pregnancy and most likely won't be here for our newborn. The other two kids are saying where daddy. I miss daddy... I'm at a breaking point!!! What's the point of being in a relationship, if you going to do everything on your own anyways!!!