This is in A# Aeolian, although I would rather call it Bb since it is so much easier to notate. That is a minor scale, so Bb minor works here over the whole thing. It is not jumping around keys, just scale degrees. When you hit the f#/Gb on the third note, that would insinuate a Gg major chord. However, considering this is a melody and not a bass line you have some freedom here. if you post an audio sample of it it would be easier to hear than look at in this way.