My doctor had me come in weekly for blood work and a weight check to monitor how I was coping during the worst of it. She's a great doctor, and she was treating my HG, but not agressively enough (she's very conservative with meds for everyone). I had to constantly ask her for better treatment. After I lost a significant amount of weight, she transfered me to a high-risk OB who then put me on more meds.
I find that I have to be really direct with my doctor about what I want and need. It means staying really informed of meds/dosages, hydration options, and your own personal limits and expectations on being treated. Sometimes doctors respond better when you bring a second person to the appointment to help argue your case. Maybe you can meet with your doctor to ask if they can do weekly bloodwork to check on iron, electrolyte balance, and organ function. Also ask about Unisom/B6 if you'd like, but you can get it over the counter if they aren't aware of it. I'm in Canada, and we have to get it by prescription here (it's called Diclectin and it's specifically meant for pregnancy. It's timed-released, but otherwise the same thing). Motherisk recommends it as a first "line of treatment" with NVP. You can also get some acid blockers over the counter (Zantac), and others are by prescription-only (like Nexium). When you're not eating much the acid burns your stomach, so it's good to control the acid throughout an HG pregnancy. You can use an acid blocker (like Zantac), and/or acid reducers (not sure which ones, but I think Nexium/Protonix??), and antacids, like diovol/tums/gaviscon, etc. You may get reflux, so these help that too.
As for the ensure...I know! The aftertaste is like a metalic-vitamin-plastic taste. If you can drink more than one, it will really help to slow down your weight loss. It sucks having to drink it, but if you can manage more without throwing it up, it will really help get the calories and vitamins you need. You still may need more than that in terms of fluids/meds though, so keep on fighting until your weight loss is under control!
Good luck and I hope you get some more relief
DD1 born Jan 29, 2010. Mod-Severe HG. Started treatment at 5 weeks. c-section (breech)
DD2 born July 23, 2012. Severe HG started treatment at 4 weeks until birth. VBAC!