i have been in france and would like to stay longer to work p/t.

i had been living here for 5 months when i left to visit the states and wasnt questioned at the airport and my passport wasnt stamped.
when i asked about a visa at the airport, the officer said, "dont worry about it, you dont need one"
i have returned and would like to stay for a year or longer and begin to work in paris.
how long can i stay working under the table? if my visa is not stamped, can i stay indefinitely without a problem upon leaving?

if i marry my portuguese boyfriend, will it be easy to obtain the same status he has as an EU member? if so, is it legal to work in france?

thank you very much.
jo