help. getting caught in a big lie

So trying to make this short..
I'm in college I failed a bunch of classes due to missing a lot of days because of my moms cancer and loosing my grandparents. 
I didn't want to disappoint my parents so I didn't tell them about all my failed classes.  I'm now retaking the classes and told my mom my school is making me redo a class because I didn't complete the prerequisites but it's a lie I just failed it. 
Now my mom wants to call the school. I think I just have to tell her the truth but now I just look even worse because I made up a big lie. I just didn't want to disappoint anyone. 
Any tips on what I should say to her. Or what do you think she will say. Would you be mad?

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors