I had similar experiences when I started, and was actually taken to task by a manager because on my FIRST DAY of employment (with no training at all or prior experience beyond volunteering with activities) I was left to wash a resident alone.
It does get easier as you become more familiar with the tasks, but the older staff will ALWAYS pick fault with the newer staff; you're too slow, you don't know how to do the tasks blindfolded, you took too long, you're not doing it the way they've always done it (usually because you've been taught a safer way), etc. Don't take it to heart, and don't let it put you off.
And yes, they are SUPPOSED to give you guidance, that's what you're there for. For the sake of not ending up in legal hot water, don't allow yourself to be pushed into anything you don't feel safe to do. If you aren't confident showering someone alone, insist on help. What are they going to do, complain about you? If they do, THEY will be in trouble for not training you properly.
Don't be afraid to approach your lecturer, too.
I nearly quit after that kind of thing too, but it does get better. As you get to know the job better, you get more respect from your co-workers as you're more able to "pull your weight". Ask questions regularly, ask them to demonstrate what they're getting you to do, and work as fast as you safely can. And whatever you do, don't stand around looking lost. If you don't know what you're supposed to do next, ask somebody. After a week or two, you'll get to know the routine and naturally know what comes next and how things are done. Until then, show them that you're a hard worker.