I've been working on this for the last 3 months.

Can you send me your audio file? I'll send you back the midi I can generate; it won't be perfect but it might be usable. See comment elsewhere in this thread.

Here's an open-source project from Google Deepmind's Magenta Project, that does exactly what you want. https://magenta.tensorflow.org/onsets-frames

There is probably something out there, but I know you can do this in Ableton Live by dragging an audio file onto a MIDI track and it will extract the notes into MIDI for you.

Automatic music transcription is the technical/academic name of this task. Maybe that can help you in your search?

MIDI Guitar 2 from Jam Origin (jamorigin.com) works well even for piano.

Melodyne or Ableton. I've found Melodyne to be more accurate, but still not perfect.