I felt like that when I first went out, but have found it gets easier the more you go out in traffic. I am still a bit shaky at major right turn junctions, but I guess that will also come in time.
You should never let the actions of others (drivers in this case) stop you from doing what you want to

I reason that the majority of drivers really don't want 15 (and a bit) stone of cyclist landing on their vehicles and so hopefully will not try and run me over on purpose...of course there's always a few nutters out there, but you can't allow for every possible senario...its better to go out there and enjoy your cycling, youv'e just as much right as anyone to use our public highways