From the little you have written about what causes you issues, my professional brain says you have a little speed on approach problem. You say you change gears last minute at junctions, but that's worth exploring a little - do you mean last minute or in the last car length or two.
What I am getting at is that distance and time are not equal when approaching junctions etc.
So if you are a car length (about 5m) away and doing 4mph, that only gives you about 2.5 seconds to change gear, but while you are looking, positioning etc. That's really tough for a learner.
But if you are a car length away doing 1mph, you've got around 10 seconds, and that difference in terms of mental processing and getting everything done is massive.
You normally should be changing gears close to the junction - that's considered best practice - but what you need is the time close to the junction to achieve everything you need, but you are in charge of the car's speed, so you can literally make the time you need. You can be a Timelord, so budge over Dr Who, your car is your Tardis.
The difference in speed use in the example above is really difficult to notice as an inexperienced driver, and you are probably instinctively trying the match other cars around you and your experience of being driven by others. But they are cheating - they have a big bucket of car control experience to call on.