As has been said, everything could be perfectly normal - stress can be a real factor though, so it is important to both maximise your likliehood but also to try to relax. I took over two years the first time, but was undergoing tests by then.
It varies by health board, but in general if you are over 35, they will consider referring you for investigation after 1 year of trying, if you are under that, they would not consider any tests until you have been trying for two years.
If you are really concerned, go and speak to your doctor.