External Hard Drive Stuck On Booting

My 4TB hard drive recently won't boot properly. It powers up, the light comes on, I can hear the disk as usual, no unusual sounds, but then the light starts flashing as it always does but doesn't stop and shows up on windows explorer as an unknown drive without telling how much space is on it. It freezes up windows explorer, I can't restart the computer unless I unplug the drive, disk repair software stays stuck searching for new drives unless I unplug it and I can't access disk management unless I unplug it. I unplugged the device without safely ejecting which has caused this, so is there any fix I could do? there are some irreplaceable files on this drive which I was in the process of backing up (what timing, eh?) - I've tried disk check in command prompt, it was sat for 3 days doing it, got to stage 5, got through almost all of the clusters and then just stopped disk checking. I did this twice with the same result again. Any help would be appreciated, thanks!