Failing classes

By semesters do you mean four classes in each or two courses taken in two different semesters? For the former, I mean, four F's/D's might put a dent in your overall GPA, but if you are able to do grade forgiveness and retake the classes, I think that could help you. For the latter, two fails in non-prereq classes shouldn't be super damaging, but whether you'd need to retake them depends on how competitive the nursing programs you're interested are and if they care about your overall GPA.

While a bunch of W's isn't going to look amazing on paper either, I don't think it disqualifies you from nursing school. Instead, it'll be something you want to address with your program and turn into a positive. You can use this experience to show how you are determined and able to pick yourself up and do something again. That's something you can't be taught easily and will need in nursing. Your experience also gives you a better understanding of what some of your patients may be going through and gives you knowledge that others probably don't have. You can especially address this if you apply to nursing programs that have an essay or interview component.

Just work hard to make great grades now and try to make all A's in your prereqs.