Practice your technique by yourself to get that down and be able to do your routine by yourself with an imaginary parnter. When you are competeting try to focus on your partner and your dancing. Try to relate, smile or someway connect to your partner and your dancing. Pretend you are in a bubble together--helps keep you mind off the judges.
Dance a few competitive dances like Int. Standard--only--not 10 dances. Get your routine or 1 1/2 minute loops or routines down and do it with a variety of music. Do some local showcases to help your nerves. Practice your routines over and over--you may have to vary them some due to floorcraft. It appears that you just need more preparatation and experience. It helps if you have a compatable partner and a good coach too.
I did a unrehearsed competition a year ago with a partner that I have been dancing with on and off for 3 years. We were unreheased and it showed. We make mistakes and the judges saw it too. So, be prepared-and do as many public performances and competitions that you can to gain experience and confidence.