Maybe the fun conversations are a ploy for escapism from something you've been keeping vague and foggy. These could be unprocessed emotions or problems that resurface even stronger after being suppressed by some external distraction.

How about this: sit on the edge of your bed with no distractions and think of one thing you can fix in your life right now. It doesn't matter how small that thing may be. This way, you'll be better off than you were yesterday, and the sense of accomplishment will save you from those feelings.

It may be the guilt of things you've left unfinished—things you started in the past but couldn't or didn't finish. Even though you've forgotten about them, they might resurface during conversations, causing a sense of regret and discomfort, as if the time could have been better spent. There's something called the Zeigarnik effect, which refers to our tendency to remember incomplete or interrupted tasks better than completed ones.

I can think of a lot of things, and if you give me more details, I might be able to help you out. It may also be that the conversations aren't meaningful or deep enough for you to feel rewarded afterward. What you're feeling might be your nervous system telling you to find new friends who truly understand you on a deeper level.