Holloway,
When I started flying, the two parts of the whole game that seemed most intimidating were talking on the radio and knowing where I was. Especially since my instructor had a magic psychic power to always know exactly where everything was.
A lot of this is simply that the human brain, in the early stages, can easily be flooded with the novelty and stimulation of flight, causing the poor thing to give up quite easily on tasks that would seem trivial sitting on the ground.
At one fairly early stage of circuit training things reached rock bottom for me when I pressed the transmit button to call downwind, and simultaneously realised that
a) I had forgotten the name of the airfield I was flying from (it was Old Buckenham, so "Buckenham Radio" was the station I should have addressed)
b) I could not spot the airfield, even though I was in the downwind leg of the circuit. (Well, it's a wide circuit for noise abatements, and a little cloud had plunged it into shadow)
My instructor was highly amused but was careful not to make me feel bad about it. As he said, these are common problems in the early stages and nothing to be embarrassed about.
It is a good idea to get a copy of CAP413, the CAA RT manual, and just practice making the various calls to yourself, using your aircraft type, airfield, etc. And as others have written, it's best to work out your message before you start to transmit.
Both this and your situational awareness will gradually work their way into your consciousness, but it takes time. Don't worry if it hasn't happened yet. One day you will suddenly realise that it's all snapped into place in your head, and you won't be able to remember exactly why it was difficult. Meanwhile your instructor, if he/she is a good one, will keep you working hard but be patient with you as well.