Well, you're in a tough situation emotionally and mentally...but I think that the decision is up to you and your DH. I'm sure your doctor can tell you if you're physically capable to carrying another baby (which I don't see why you couldn't), but there's a lot that goes into planning for an HG pregnancy, including finances, childcare, your care/protocols, etc. You might start by checking out some reasources under the "mother" section of this site. Like this link on preparation for HG:
If you don't have an extremely HG-aware/proactive doctor, and you live in the US, you can try the referral network: http://www.helpher.org/mothers/referral-network/index.php OR If you're outside the US, you can use the forums on preparing/finding doc's too.
I'd plan out your protocols in a lot of detail, with contingency plans (like "If A happens, then B, if B happens, then C, etc.), and see your doctor to discuss it/get meds before you start trying to get pregnant.
Good luck, and we're here if you have questions!!
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!