Things seem to happen fast in a P92 in the circuit don't they! As hard as it is to believe now, what the others say above is true...it WILL just come to you as your brain learns to subconsciously manage things. Getting trimmed early and thinking/looking ahead is good advice, both for straight and level on downwind (I trim before turning downwind) and when descending on base. It's one less thing you need to concentrate on.
I struggled with radio calls and lost the plot in the circuit when trying to do them. This is one thing that's really easy to practice on the ground. Try to practice them every time you do something else complicated like driving a car. But don't practice them while you are just driving along, do them while turning a corner at traffic lights or going through a roundabout while giving way to traffic. 50 metres before you get to the corner think about what you are going to say, decide which leg you are turning and which runway ("Wagga traffic, Tecnam xxxx, turning downwind, runway 05, touch and go, Wagga"), then say it out loud while making the turn. On the next turn call the next circuit leg. Be careful, it's surprising how much extra concentration it takes even while driving a car. But it will quickly become second nature and another thing you don't need to concentrate on in the circuit.
I used to do it driving a loaded truck. I would decide on the call while slowing down for corners/roundabouts and managing speed, throttle, brakes and constant mesh gear changes. Then I'd make the call while turning and slotting into traffic. Next time I flew radio calls were a breeze. The idea is to train your brain to do several things at once.