Heat headaches

We’ve been ttc for 2 years, almost. I had a miscarriage last Fall, but when I was pregnant had all the same really early symptoms I would normally leading up to my period except butterflies—that kind of gut feeling. Well, I’ve overanalyzed everything since, but one thing I’m curious about is heat headaches. My whole family has this amazing ability to stay in the sun and heat all day long (while hydrating properly) without any side effects like most of my friends do. In the summer, being a teacher, it’s not abnormal for me to spend 6-8 hours in the sun every day gardening, napping, reading, walking, etc... Well, this last week, I can only last about 2 hours outside in the sun and heat without getting a massive headache. Last night it turned into a migraine. Today I barely lasted 1 hour in the shade. Has anyone had this as an early sign of pregnancy? The sudden inability to handle heat? I’m trying not to read into anything else, but this is just so not normal for me!!