OTS is more or less a diagnosis of exclusion. There is no test to tell you that it’s OTS. But you can make a good guess if you look at the training and overall stress of the last weeks/months. What’s important is that it is not only about training but about stress in general. You can get burned out even without training. So if you can rule out any other health issue, then overtraining is something to consider. How severe it is, is hard to tell.
What I found the best approach is NOT to stop with exercise altogether. But shift away from structured training. And most important: Do something different! If you did mostly endurance training then it’s time for some other things. Anything that is fun and not too stressful. Some easy climbing or bouldering. Something playful. Dancing… Core and strength training. You can actually go pretty heavy with the strength training. But only short and not to failure. This can give you a good hormonal boost, that helps with recovery. Go for an easy walk in nature. Get a lot of sun. Meditate. Get enough sleep. Eat healthy and enough. Socialize (what possibly this times)…
You will feel it when you get better. But you will not wake up one day and feel totally recovered. It’s more gradual and with some ups and downs. But it can be a good experience, that can teach you a lot.
So take it easy and enjoy the process.
If you are concerned that some other health issue could be contributing, I’m happy to help.