I realised they wanted to be alone together, so I felt very awkward.

Answer: Option C

Cumbersome : large or heavy and therefore difficult to carry or use; unwieldy.
Unwieldy : (of an object) difficult to move because of its size, shape, or weight.
Embarrassed : feeling or showing embarrassment.
Clumsy : difficult to handle or use; unwieldy.
Awkward : causing or feeling uneasy embarrassment or inconvenience.

Synonym of Awkward is Embarrassed