Have you altered your diet recently?
Have you recently started a new type of training regime?
Did you drink less water than usual?
Have you recently enjoyed less sleep?
Could you be in the early stages of some kind of cardiovascular issue? Do you perceive yourself to be someone with early onset problem X?
Did you possibly react to an increase in room temperature, perhaps because the intensity of the training you are doing, pushed you to a level, that more recent lower levels of heat may have not caused, as Andalucia in the shade, must still be quite hot this time of year?
Have you increased the intensity of an existing training regime?
Do you think 3-7 days off may help, or if you have started a new routine of some kind, or increased the intensity of an existing one, do you think your body could get used to it and allow the problem to to lessen over time, or do you think it might be something that could occur again?
I ask that last question, to gauge whether your judgement of the problem in hand, leads you to believe it might be a temporary problem, or caused by one or more constants, as then you could either use a suck it and see method, to see if the problem starts to desist, or if it is caused by one or more constants, in which case try this.
Add some kind of compensatory factor into the equation, like a bit more Carbohydrate, or more water, or a slightly lower level of Cardio as examples and use one change as a testbed, to see if after a week or two, it prevents the issue you have from reoccuring. If the problem still persists, reverse the change you implemented and replace it with another, like say if you added Carbs but kept Cardio the same, cut Carbs back to the previous level and then reduce Cardio as an example.
This method allows you to isolate a singular change to assess it's efficacy and then by reversing the change and replacing it with another, when it has no beneficial effect regarding your problem, you continue to replicate the original circumstances causing the issue, with one solitary amendment to the circumstances each time, until you find one change or tweak that solves your problem.
However the problem may desist over time, if it is something the body just need adjustment to.
If the problem does not seem to start lessening, or your try the change isolation method I described and you're still struggling to effect a positive outcome, consider the point about early onset condition X and consult a medicla proffessional.
The exhaustion could be something like Chronic Fatigue Syndrome, if attempts to improve the situation keep faltering, so consider a non-invasive medical intervention like a scan, general checkup etc, as a third option should a suck it and see, or change isolation principle not work.
Hopefully there's food for thought there, but any other insight you can give, either relating or not relating to any of the questions I asked, please feel free, as there may be other suggestions for myself or possibly others to offer up