Always happy to help whenever I can!
Think of this as learning a new language... You're not going to get it all right away. It's easy to get frustrated, and when you do, it's time to put the bass down for a bit.
Glad to hear your actual hearing isn't the problem. Just like learning anything else, hearing the chord changes takes practice. I wouldn't worry so much about transcribing bass lines yourself, there are some good resources out there for songs that people have already worked out. Do you read tab? If so, check out Invalid Link Removed. They've got a big database of tabs (more guitar charts, but a lot of bass tabs too) that people have already charted out. They're not always 100% correct, but generally they'll get you close. If you read music, check out your local library... Maybe they have some songbooks that would be good. You'll be lucky if they have actual bass books, so look for piano books. They'll have chord changes included and you can also see what the piano does in the left hand which is usually the bass line, or close to it, in pop songbooks for solo piano). Guitar books will have chords marked out which may still help, but they won't usually chart out the bass lines.
Start simple too. You're not going to be able to work out a Victor Wooten or Matt Garrison song quite yet. Lol Off the top of my head, I'd suggest maybe starting with something like some Beatles songs... More simple basslines that are still super catchy and easier to hear. Maybe some Green Day? Quicker bass lines but usually a lot of 1/8th or 1/16th notes that stick to the root of the chords. Ooo, here's a good one... Try Sweet Home Alabama from Skynrd. It's a simple V-IV-I line through the whole song. Once you get used to connecting the dots on the simpler songs, the more complicated bass lines will get beneath your fingers much easier.
It'll take some time, but with practice and patience, you'll get it. One thing that really helps me when I'm learning a new song is to listen to it a few times before I even pick up a bass. Get familiar with the song first so you know the groove and what's coming ("okay, here's where it goes to the chorus."). After that, I tend to pick the song apart... Example: I'll focus on the verse groove first, playing it until I've got it down and then I'll move on to the chorus and learn that. It's easier to take in bite size chunks rather than trying to learn the whole song all at once.
5sg.