Very basic question re: baby blanket

I have been working on a very simple blanket for my new baby (due in March) using circular needles. And last night out of the blue (I was very tired) I ended up knitting the two sides together…I have no idea what I did differently! I started the blanket over this morning and I still can’t figure out what I’m doing wrong - when I start the 3rd row of the blanket I am still knitting the two sides together. Any ideas/suggestions???

Welcome to KH!

If you’re using circular needles that’s easy to do. Make sure when you turn your work to do the other side that the yarn is coming from the left hand needle. If it’s coming from the right needle it will join when you knit that first stitch.

Yes, just don’t forget to turn at the end of a row. Make sure your sts aren’t so crowded together you can’t tell.

grab a couple of stitch markers or use an empty spool for thread (i do when i’m working with smaller needles, i end up using one of my plastic bobbins for my sewing machine) so that i don’t accidentally stitch the two sides together.