Passing your Driving Test

Hello 

I have now been taking lessons for just over one year and I have taking the test twice and failed both times. I am driving an automatic as I have enough things to worry about can't deal with a clutch and gearbox as well.
My instructor is lovely and really patient with me but he says he now cant teach my anything else and doesn't really get why I didn't pass last time, because I screwed it up. 

I find driving itself a little stressful and have found myself hesitating a little because I check things, I have slow proceessing speed and don't always process what I see (and therefore don't recognise I have seen it) so I often double check things, hence the hesitating at juntions/roundabouts. 

Big problem with driving tests is that I get very stressed/nervous and then my brain takes even longer to process things and boths times I failed my test, I have done something stupid (never have done it on lessons or anything) and then fail the test on a serious fail. For example last time examiner said to go straight ahead on a double mini roundabout without stating the destination writen on the sign (bath, bristol, etc), this roundabout has a two exits in the roughly straight direction, one slightly to the left and one slightly to the right, as he had given me no clue as to the destination I hesitated, couldn't work out which way to go, paniced and picked the right hand one but I forgot to signal right so he failed me (apparently the one to the left was straight one and I wouldn't have needed to signal as it was straight on).

Anyone got any ideas on how I can help myself work on these issues and pass because would really love to be able to drive.