Take a week off from training, see a doctor.

Agreed

And make sure you are eating enough.

Sure you can be overtraining.

That just means you are piling more of a load on your system than it can take.

Doesn't have to be only an exercise load, but diet stress, daily stress, nutrient deficiencies, lack of sleep for level of activity, ect.

All those things can cause a body that might otherwise NOT be stressed too much, to become stressed too much and progress stops and many times goes backwards.

I'd suggest start getting your resting HR every morning and tracking it. Especially when you give yourself enough rest as hopefully a baseline.

Then when it starts to move higher you know you are doing it again, before other worse symptoms start occurring.

That's usually more immediate than lifting observations, but even there, if you stop maintaining weight you were doing before, indicates wrong direction.

Sorry, but was HR stands for? Heart rate? Do you mean I should track my heart rate every morning?

Correct. And RHR, Resting HR. Before you start moving around, have watch right there and actually count for 60 seconds being calm. If alarm wakes you up like me, might have to have a few more restful minutes to calm back down too.

But that is an excellent indicator of the body being too stressed.

Problem is you need a baseline to see movement. You could get 60 right now and think that's great. But what if it was 50? Or could be 45?

You've undoubtedly done some intervals.

What allows you to push so hard on the hard part?
The fact you had a rest period in between hard efforts. How well would you be able to push that hard if you had no rest time? Not much longer, your performance would suffer and pace would drop as heart rate slowed down because you just can't keep pushing that hard. Your body can't do it no matter how strong your mind is.
Ever made the rest time shorter, same effect eventually happens, the hard efforts near the end aren't as hard judging by HR and pace, though it sure feels like you may be pushing just as hard.
And the reason you want the hard part to be really fast and high HR, is because that is actually what causes the overload that requires improvement. Not just a hard effort that is stressful only.

Exact same principle applies in general to your workout routine.
But from day to day usually. Hard enough effort maybe even takes more than 48 hrs to recover.

To really be able to push well on a hard day, you must have adequate rest on the easy day to be able to do that.
Day after day of pushing hard may feel like you are really doing some good - but not as good as you could be doing if you gave enough rest.

And you'll likely never notice that difference until you do it.

Another example because I've trained people doing it already.
Go out for a run with so much time available, say 45 min. Go out way to fast because they want to make it hard, and slowly but surely pace keeps dropping and they are dying at the end.
But it really feels like they accomplished something because they are so tired. Great high pace. At the start. Over all, not great because they slowed down so much continuously. But compared to previous runs, maybe even improving. Slowly. If at all.
But if they held to a reasonable pace the whole time, they actually would have been faster overall. And training in that manner would lead to faster improvement actually.

A week can turn into that same thing. By the end, you aren't doing as well as at the beginning at the same effort. You'll end feeling tired, thinking it was a great week, but it could have been better for actually making improvements.