Go see your GP hun
Then something to maybe help once you get home if you need to try and go.
Sit in a nice warm/hot bath for a bit when you feel the need to go next time. Try and relax as often the worry of what is to come causes us to. And then nip out and sit on the loo. Put your feet on a small box so they are raised off the ground and your knees are higher than your hips. Then try just letting things happen. If you need to stand up for a minute then do so, and sit down again with feet off the ground. Or get back in the bath to relax you a bit till you are about to go.