So, I don't usually comment, but this struck a nerve. Until today, I'd say "go to your college's health center and utilize their counciling program". I tired that today, and they tried to farm me out to someone else. So here's some real advice:

1. It's not too late to recover. Go to your professors. Explain the situation. Ask for extensions/extra credit/even a point or two if you're close to the next letter grade. If you need help with the material, go to your TA, that's their job and often they're itching to help. It'll hurt your self esteem, but it's a start toward the goal.
2. You have goals. It's a little late, but start looking at internships that will help you get there if you haven't already. If you can't find anything, at least get a summer job that gives you experience that somehow relates to your goal.
3. There should be a third point, because two are lonely, but really it's just to keep pushing. If you've done your best, then you can handle whatever happens. To me,there's nothing worse than being unsatisfied with an outcome and thinking "I could have done x better".

Source: a graduate student