I do agree it might be anything, also your body knows you are back home at your safe place, therefore if you need any medical assistance you rather get it here than abroad. At my first trimester I always used to feel okay at work but as soon I reached home is like all the symptoms came at once.
I had the exact same thing! I did a blood test and turns out I’m low in iron! Have you had your bloods done recently?
It might be anything or be honest. I've also had a bit of a dream pregnancy but every now and then I feel absolutely shattered for a day. If you've been very busy on holiday maybe it's just you needing to slow down and have a rest. See how you feel and keep an eye on your temperature.