Feeling depressed

I feel for the past few weeks things weren't going as they should I've been working hard at school and don't get the results I used to like last semester everything was going well straight A's in all my classes and now I dropped to C and I struggle at managing my teams and not getting hours/shifts at work.. I feel from maybe last friday I am falling into depression I've cried during the weekend and lately after my midterms the subjects are getting harder for me to pick up instantly like before and I don't have the courage nor in the right state to change jobs and registered for a tough math summer class this summer to complete my studies or else I'll be even more behind and I want to graduate and not drag any longer.. Even when I try to do anything I have no more energy even fun things aren't fun anymore