That is wonderful! Distractions are a good way to stop anxious thinking, and with going back to school, your mind was occupied with other things.
As far as the deep thinking, and questions you have about life, I think some things are just better left alone....as I always say, 'it is what it is'. You could say these things just aren't meant to try and figure out. Because if you think about it there is truly no one answer.
Find a way to have meaning in your life---it doesn't have to be nobel prize winning meaning, but something that makes you feel good about life. Taking care of a pet, gardening, volunteering, or any sort of hobby. Doing something like that will distract you too.
And don't ever feel worthless, because you're not! And you are worthy of being happy, so don't be so hard on yourself----thoughts are just thoughts----and you can change them too!