I am currently off sick with stress/depression/anxiety/mania and have been for the last 4 weeks. This is my third time in 5 years but I am bipolar so all part of the illness.
I suspect the guilty feelings/bunking off school is common. Certainly, I feel that way and have had those feelings on previous occasions.
Stress, nervous exhaustion is real, so I would try not to dwell on the guilty feelings.
I think it is a positive sign that you feel guilty. I would interpret that as you have got in there early before things could really get out of control.
I have had two full on breakdowns in the past, probably down to chronic stress but you can never be sure. I know others on here have been through that hell. I am sure we are all in agreement it is not a nice place to be.
Hope you start to feel better over the next couple of weeks.