Ég á ekki eftir að strauja fleiri föt í kvöld, því ég er of þreyttur.

Here ég á ekki eftir að strauja... is an idiomatic way to say that something is not still ahead for the speaker to do.

In this sentence, it means something like:

• I’m not going to iron any more clothes tonight
• I don’t have any more ironing left in me tonight
• I won’t be ironing any more tonight

The positive version, ég á eftir að strauja, often means:

• I still have to iron
• I have yet to iron
• I’m still going to iron

So adding ekki makes it negative: I’m not going to / I won’t.

Because á is the finite verb in the clause, and in Icelandic the finite verb usually comes early in the sentence, with ekki following it.

So:

• Ég á ekki eftir að...

not

• Ég ekki á eftir að...

This is very normal Icelandic word order. The negation ekki comes after the finite verb and negates the whole idea:

• I do not have ahead of me to iron more clothes tonight
• more naturally: I’m not going to iron more clothes tonight