Oh I am so sorry about the protein dilemma. I am struggling with the same thing. They say, eat more bananas and more protein (I'm also really low in potassium and vitamin D for that matter). But even the thought of food makes sick.
Someone suggested beans to me, mixed with a little salsa and sour cream. I wasn't sure about it at first, but I ended up eating a TINY TINY amount of it...like maybe 7 beans in the mixture! Ha! But I was able to keep it down anyway. I know that so often most food suggestions just sound horrible, but on the off chance that one works, I'm suggesting it.
I have licked straight peanut butter off a spoon...just kept it by my bedside and licked a little every so often.
And finally, the protein shake. Yeah, I keep it down sometimes and sometimes not. So I don't know how to make it more appealing. I use spirutein (vanilla) and mix it with lots of orange juice and 1/2 a banana. I wait till I am really thirsty and the orange juice seems to be a little refreshing. But you never know how your stomach will react 15 minutes afterward. But I just keep trying.
What about quinoa? I'm pretty sure it is a complete protein...also full of fiber and an all around superfood. I know some people make it into a cereal. I've only had it for dinner as a side dish mixed with peas and corn...but maybe there are some palatable recipes out there for you. I may try it as a cereal this week.
If you're super duper desperate and happen to have the resources, a holistic or naturopathic doctor might be helpful in getting you some bio-identical progesterone if they think that's the HG culprit. This is the route I've taken and, though I am not cured, my husband would say I am MUCH better. One of my doctors believes that HG is the body rejecting a fetus when it doesn't have enough progesterone. Often the baby will get the extra progesterone you're making but there won't be enough for you and so it continues to be out of balance with the other hormones and makes you sick.
Regardless of the cause or how long it takes to stop - I am so sorry. It just really sucks. I guess we just survive each minute at a time until we find relief. I'm due in 5 and 1/2 months and my mom says, "Well, at least we KNOW it will be gone in 5 and a 1/2 months." Sadly, that's my only inspiration right now. *sigh*