The drip pan has been dry for more than two years. Water from the a/c
normally flows directly though the waste water system in my house.
Water dripping from a different pipe into the large drip pan under the
unit is a new thing.

Can I unclog the primary myself or do I need to get someone in to take
a look.

I am mostly concerned about the puddle accumulating right outside my
back door which is getting quite big now.

A/C is only 4 years old so is not junk