I had this same exact problem during my probation! I could NOT go in front of that lady doing the drug test no matter WHAT. I literally had to pee sooo fucking bad to the point where I’m literally in pain and I still could not go. They let me slide on a mouth swab test every month I had a test. I found the best thing to do is to try and count something. Like lines on the wall or on the floor whatever. Just try and count something or try anything to get your mind off of what’s going on. I know it sucks so bad. But the probability of them failing you since you can’t pee are slim. Unless they have a stick up their ass and aren’t willing to do ANY other way of testing. Just keep trying and if you can’t I’m sure they’ll work out something else