When to be concerned about decreased movements?

I’m only 18 weeks and Ik it’s either after 28 where movement becomes important to discerning the health of the baby, but lately the baby’s movement has calmed down? It’s odd I always notice there’s a burst of movement for a few days at certain times but then it calms down and it’s like I never felt any movement at all.

I just get worried, I dislike going to the ER bc the bill is always pricey and dropping $200-400 just to see if my baby is healthy is ridiculous and that’s with health insurance. I already have bills with the hospital and it sucks that it has to be that way ;(. My next ob appointment isn’t until next week. Any reassurance anyone can offer?