I think they can start very early, even around the time of your missed period. I am hoping to conceive soon, and I often wonder if my emotional days are early signs or just PMS.
I recently delivered, and looking back, my mood swings started around week 6. I would get so angry at small things and then start crying. It's completely normal, so just be gentle with yourself.
They literally start before you even see that second line on the test, haha! I am in my 3rd trimester now and still crying over spilled milk, quite literally. It's a wild ride!
They can start in the very first trimester as hormones fluctuate. When I registered at my hospital, the staff was very supportive and explained this clearly, so feel free to ask your doctor if it becomes hard to manage.
They can start as early as week 5 due to the sudden surge in hormones. However, if you feel extremely overwhelmed or depressed, please speak to your doctor as mental health during pregnancy is so important.
Mood swings can start in the first few weeks itself because of hormonal changes. But since hormone levels can also be affected by thyroid, make sure you go for regular doctor follow-ups and blood tests.
According to my pregnancy tracker, those wild hormonal shifts can kick in as early as week 4 or 5. Tracking my mood on the app really helped me see the pattern and manage it better.