neanie, as much as people may disagree with me, I think the only way to see steady progress when your hair gets to shoulder length is by keeping your ends from enduring trauma by sealing and protective styling and by dusting regularly so that you can nip splits in the bud. Low manipulation also helps if you have fine, weak strands.
The reason a lot of people seem to show good, steady progress till they get to shoulder length is because up until that point, the hair wasn't rubbing against clothing and so while it might've been exposed to the drying air from not being protective styled, at SL comes another assault comes into play: friction from clothes. What's more, your hair's ends are so much older and worn out--especially if you've been holding onto them over the course of your journey, so there's no way they can be full if they haven't been kept tucked away and the damage that occurs at the tip hasn't been prevented from wrecking more havoc by being snipped away.
So my advice would be to get into a habit of dusting a little regularly and sealing/protective styling. You don't have to be able to do a bun but you can wear a phony pony so that your ends are hidden in plastic under the pony after being well moisturized--as your protective style. Or you can wear Frencb braids so ends are tucked away. Or you can weave your hair (low mani helps) so that it's tucked away and out of sight. Not seeing your hair or messing with it has a way of inspiring folks because they get to see the progress they are making after some time has elapsed and come to realize retention was the problem because hair is definitely being sprout out at the scalp.
As crazy as my suggestion sounds, don't knock it till you've tried it. It's not as if you haven't been practicing good hair care, but obviously something isn't working. So why not go out on a limb and try something that you haven't tried yet: regular dusting and protective styling. Look at people who believe in regularly dusting and see how full their hair looks and how well their hair is growing. If you think about it, what good comes from holding onto ends that have had some of the whole torn away?
This to me is just gross and reminds me of a rat's tail:
^^This lady would have hair that'd be worth looking at if she's snip off that ugly long tail and keep the bulky part. She's still have longer hair than most and it'd be so beautiful.
These heads on the other hand are more appealing to me: