Beautiful pattern stitch!
Cast on 37sts for your swatch. The first row uses 37sts and ends with 41sts.
The rows alternate, odd rows 41sts total, even row 37sts total if you do one repeat across. The center stitch repeat changes too: odd rows 20sts per repeat, even rows 18sts per repeat. I'd just give it another try, counting sts after every row to make sure the row ends with the correct number. If the pattern looks off, you may need to go back and name the stitches across the row to check for a missing step.