There is no gas shortage...

Why is the dollar declining?

Lack of foreign investment in this country.
Its the opposite of the problem we had in the 80s, where U.S. dollars were buying Japanese cars and consumer goods but Japanese investors were buying dollar denominated assets and backing dollar denominated investments.
Now there are more attractive investments overseas. We keep buying foreign made goods but our money isn't coming back here, its staying overseas.

Our trade policy is killing us.

Well now that the dollar is weak there has been a lot of foreign investment in our real estate, for what its worth. An office building in DC just set a record selling for $875/sf to an Irish investor (beating out other bidders from Australia and Dubai)