Trouble Mixing/Mastering This Song (Clip Included)

[pjm]

Hi guys, I am having trouble mastering this song. The genre is sort of like a dark symphonic indie, or something, not sure exactly how to classify it (This is not a composition or recording question, just mastering)
I think the mastering sounds good on my two pairs of headphones. But off my computer speakers it doesn't sound very good, and off my external speaker it sounds terrible.
How can I make the finished product sound better via mastering?
Thank you so much for your help and suggestions. : ) <3

Edit: Also, if you know any people or services I can send my songs to to get them mastered over the internet (besides LANDR), I am willing to pay, please send me their information or website!
Edit2: I posted the uncompressed file farther down.

[JosephSelahJr]

I'm no mastering master. But your volumes seem...

[donkeytugger]

Good song by the way! It's difficult to work o...

[m@RV]

What did you use as a reference track? (PS I ag...

[pjm]

Thanks everyone for your feedback! Here is the ...

[D3Mens]

Nice song, unfortunately the uncompressed versi...

[donkeytugger]

Madma wrote:Nice song, unfortunately the uncomp...

[m@RV]

pjm wrote:Thanks everyone for your feedback! He...

[D3Mens]

Here you have a preview of my master (mp3 + wav...

[mrphenom]

Hi, since other ones did mastering, i did also ...

[pjm]

Hi guys, Thanks so much for all your help! I'm ...