There is a large lump in my abdomen just below and to the left of my naval. I am 6 weeks pregnant. What could it be?

Have a OB MD check. Definately, get examined by a OB md to find out.
Hernia or lipoma. You are only 6 weeks pregnant, lump is not related to your pregnancy.It may be an umbilical hernia or lipoma. When you see your OB doc soon in the next 3-4 weeks , inquire about it. It is very difficult to tell you now without seeing the lump with the location as well.