I've knit for years, and I can admit I still have challenges
with correct stitch counts on some projects, like lacework scarves for example.
Here's what I told a new knitter at our recent South Sound Knitter's Guild meetup:
"Think of knitting like taking a bunch of kindergarteners on a field trip! Everytime you get off the bus, and get back on...you need to do a 'head count'!"
And knitting can be just like that! At the end of EACH row...I do a "head count"...to make sure I haven't lost any children, I mean 'stitches'!
The use of stitch markers between repeats...or in your case maybe between every 5 stitches...makes the 'head count' quicker to count up!
You don't want to lose any kids, and you don't want to pick up anyone new, either!