I understand that it might feel distressing that you're losing interest in the things you used to enjoy.
Irritation, loss of interest, reduced social interactions, lowered levels of energy can be significant of a few different problems. These could also be caused by an increase in stressful situations, or prolonged engagement with high stress situations. If your job or home life is stressful, or if you've had recent difficulties, these might be causing these changes.
Taking care of your mental health is just as important as your physical health, and needs a holistic approach.
Unfortunately, with such few details it's difficult to say what might be troubling you.
Next Steps
consult with a psychotherapist or psychiatrist
Health Tips
try not to diagnose yourself. maintaining a healthy diet and exercise routine might be helpful but aren't the only answer.