I'm sorry to hear you're having a rough time. I was in a very similar position awhile back. Eventually it led me to get a new job outside of direct clinical research. But in the meanwhile, here are some things I did that helped me while I was still in that job:
1) Make friends with other clinical research assistants/coordinators in other labs - they can help you navigate ordering supplies and sometimes it's good to just have someone to vent to who can understand what you're going through
2) I'm assuming you're recruiting patients in clinics? The clinic manager is your greatest ally. They know exactly where each physician will be and if you need something they can definitely help make it happen. I left my job but I still send update emails to the clinic manager I used to work with because she was genuinely just one of the nicest people I've ever met.
3) Ask your PI if there's room in the budget to hire an additional person. If you have someone else there with you the work might be more manageable.
4) If you feel comfortable, develop some relationships with other PIs/admin staff in your department. They might be able to help you out and give you advice on how to handle certain things that you're uncertain about.
Unfortunately, what I discovered was that training is really lab dependent, and if you're with a PI who hasn't established protocols already, or has current research staff, it can be difficult to navigate. But, one other thing I discovered is that people are more willing to help than not. If you have a question but don't know who to ask, don't be afraid to reach out to a person in the department you're targeting, and ask them to direct you to the appropriate person. Best of luck, you'll definitely get your footing once you become more established.