I don't know if this applies when one is pregnant but I have what sounds like the same sort of difficulty. On some days and only on some days and usually several days in a row I go to bed and feel hungry and my stomach is somewhat painful. I get up and eat both a starch and a protein. I eat both because over the years I've found that sometimes one or the other works. Sometimes I still feel hungry but most of the time my stomach is comfortable enough to go to sleep.
My theory is related to my blood sugar level. When my blood sugar is lower than what my body is used to it my body tells me I'm hungry. I am now pre-diabetic and the meter doesn't seem to back that up. But I can't figure out any other cause. I've asked the doctor about it. I've had an upper and lower g i exam. I'm healthy. Eating helps. So I eat. I stopped trying to figure out why and just do what helps.
Have you tried having a nutritious snack before going to bed or getting up and eating something when you realize you feel hungry?