It sounds like you should be working all these sts into the same
group of 3 sts. K3tog but don't drop the stitches from the left hand needle, yo, and then knit into the same 3sts again. Then drop the stitches from the left needle. You won't decrease any sts this way. You'll have 3 new loops over the right hand needle, 2sts and the yarn over.
It's like this video:
For slip 1 WYIF, move the yarn to the front, slip one purlwise from the left to the right needle. Since you're at the end of the row, turn, pick up the working yarn and proceed with the stitch pattern for the next row.
What are you making? Can you give us a pattern name or link to the pattern?