I seem to have lost interest in the things that used to make me happy. what can i do?

A few ideas: Perhaps you're depressed. Loss of interest or pleasure in activities can be a symptom of depression. Your doctor can help sort this out. If this is the case, there are effective treatments. But don't delay, early treatment tends to have an advantage over treatment that comes after much time has passed. The other idea is that maybe you could explore something new. Following your curiosity is good.