When did your baby's movements become really regular and predictable?

I'm 20 weeks now, and started feeling little fluttery movements a week or two ago. While I'm generally feeling at least one twitch or flutter most days at this point, it's not really regular at all. I know that you're not supposed to be doing kick counts or anything until the 3rd tri, but how worried should I be that I'm not feeling super regular movement? Or that the past day or two, it's felt a little more "muffled" than it has been in the past?

Could it be that the baby's rolled over or something, and is now kicking somewhere I can't feel it?

So I'm pretty sure I'm worried over nothing, but being a FTM, you know how it is!