What is the Dorian Mode in music?

So I have a song in A minor where I raise the 6th note in the scale but only once. The whole melody goes ok with F but only in the main theme, only once it goes F shard and then again just F. So for the entire song I have raised the 6th note F only like 5 times, five F sharps in the song. Does it mean I have a Dorian mode? Do I need to raise it all the time when I play F or just once is already enough to consider it as a Dorian mode?

2017-04-11T00:37:33.809Z