I feel terrible for the one person who showed up, especially if they were not warned beforehand that the other two were bunking. I get you have anxiety and possibly psychosomatic bodily reactions, but you ideally need to get that treated, no point in being at uni if, as you say, you're skipping all of your classes. And especially as it was ungraded that was a great opportunity to face your fears without worrying how it would impact your grades. It's far better for you to take an interruption of studies and seek professional help because once you enter the workplace you can't just not go in due to anxiety all the time, you'll be fired or won't pass probation etc. so better to deal with this now than let it fester.