My Schengen visa is expired but I'm still here in Poland. Can I go out in the country anytime even I applied for the extension of my Schengen?

Short answer:

From the question I assume you are talking about an

• extension of a residence permit issued to a spouse of an EU-Citizen

You have applied for the extension, which has not yet been issued, and the previous permit has in the mean time expired.

The present permit is a

• residence card for family members of citizens of the EU or of the EFTA Member States

As a general rule as a spouse of an EU-Citizen you should have no problem reentering Poland.

It would, however, much simpler and more reliable, to go with your Polish spouse to the local authority and ask.

In most cases they will know best on how to deal such a case properly.

Long Answer:

The polish government site (Ministry of Family, Labor and Social Policy) offers an english page with extensive information

• Registration and residence permit

If the stay in the territory of Poland last more than 3 months:

family members of citizens of the EU or of the EFTA Member States who are not citizens of the states are obliged to obtain a residence card for family members of citizens of the EU or of the EFTA Member States, which is issued for a period of 5 years as a rule (or for a shorter period depending on the period of the planned stay of the citizen of the EU whom a family member joins or with whom a family member stays in the territory of Poland.

Note:
This page seems to have been dated as the 9th of August 2016