CT Thorax + abdo + pelvis with contrast

Hello.  I've just joined this forum. I'm a cancer warrior. I was diagnosed in January 2017. I had a strawberry sized tumour which was ER +.  I've had chemo, lumpectomy with full anxillary node clearance and radiotherapy. 

I've got lymphodeama and have also developed arthritis. I was fit and active before my diagnosis - riding my bike 12.5 miles every day. I've put 3 stone on too, but I just can't stick to a diet.  I'm depressed with it all.

My gp has referred me to the gastro consultant at the local hospital, who has ordered  CT Thorax + abdo + pelvis with contrast to investigate my unexplained left-sided pain.

I'm not worried about what they find, i don't think it's sinister. I'm just wondering if I'll have to get naked for this - or can I wear loose-fitting clothes?  And what's the contrast for and where do they inject it?

Thanks for letting me join.  Thanks for helping me!  xxx