Also, what type of flatiron are you using?
I used to get really weird split ends like that too a while back. I would sit for up to an hour picking at them and cutting each one of them off. It was like I was determined to get rid of them all which was pretty impossible, lol. I ended up doing a BC and since then, I have been moisturizing my ends everyday and sealing with oil (no questions asked), only rinsing with lukewarm water, and doing a final rinse with apple cider vinegar to close the cuticle of my hair when I'm done washing or co-washing. I don't have those in my hair anymore (not saying I have absolutely no split ends, just not really any that I can see).
The reason why I ask what type of flatiron you use is because about 4 years ago, I invested in a tourmaline/ceramic flatiron that straightens without as much heat damage. So now, the infrequent times I do flatiron my hair, it doesn't snag and pull my hair or overheat, causing split ends.
It was pretty expensive (around $90) on folica.com, but it was sooooo worth it!!
(I'm relaxed by the way)