Wiland; Please consider talking to your original lender about refinancing options. Also, is your HELOC through the original lender on your first home? That may be a good bargaining point, and actually you may consider asking to take on the debt for the short as part of your HELOC payment. This is an unsecured loan option and is a risk for the lender, but one that they are more and more likely to accept as it means in the long run they are NOT short the money for the home sale.
It sounds like you could actually use a good session with your lender, which is free, to discuss the options you have available to you BEFORE your original mortgage goes into distress. Maybe they can adjust your payments to something you can manage until it sells, maybe they can consolidate. Take the time and make that appointment; it will be better for your credit score in the end.