Not really a lot I can add to this that hasn't already been said. What I would ask is what aircraft are you doing your circuits in? Not that it's wise to change whilst learning, but I found in a Robin HR200, after a couple of practices, I was able to stay well ahead of the aircraft, but when I then did my check out on the PA28, it was a bit harder as the aircraft was quite a bit quicker.
One thing I found helped immensely is to get the radio work out of the way before doing your BUMFICH (I guess this is used everywhere?) checks.
For example, instead of waiting to turn downwind before you call downwind, call 'G-ABCD, turning downwind, Runway XX' as you make your turn. That way, as soon as you level off, you can put the carb heat on, check your breaks are off, your undercarriage is down and locked (probably not necessary for you right now), Mixture's fully rich, Fuel sufficient, instruments alive, canopy closed and locked and harnesses secure, then put carb heat back to cold. ***(Applying carb heat at this stage MAY differ between different aircraft)***
Once you've done all this, you'll have a precious 20 seconds or so where all you have to think about is flying straight, before starting your crosswind leg and descent.
Always memorise your acronyms so you can recite them as you do them, and the whole thing should take not more than about 10 seconds.
If you haven't done your first solo circuit yet, don't worry. When you do, it's a memorable experience and you'll know that you've got it sussed. Just remember, it is easy to lag behind the aircraft, so ensure you're always one step ahead. That way, you won't have a problem.
If you think you don't have enough time, you may be doing the circuit too tightly, but ask your instructor.
With regards to groundschool, it's defintely worth doing to recap your knowledge. Take some online quizzes (PPL Cruiser has a good question bank), and I downloaded an EASA PPL Exams application for my android device, which proved very useful for revising on the go.
Best of luck with it all
T