I think it depends on the policy of the program you're in. In my program, if you get a D+ or below at any point in the program, you're out. And if you get a C or C- you're on probation the following semester. If you get another C or below that following semester, you're out.
I'm struggling too, so don't worry; you're not alone. I've had to adopt the mentality that I just have to do whatever it takes to pass...I've given up on trying to be an A student. And honestly, you don't have to be all that concerned with grades anymore once you're in an OT program. Again, just do what you have to do to pass. You can do it; you wouldn't have gotten in otherwise!