did you try the mattress stitch which salmonmac gave you a link for? if you lay your blanket down on a flat surface to do it, with lots of light.....should go smoothly.
If it's not, rip out and start the sewing over. It will be worth it to have a nice finished project.
My mother once gave me a squares lap blanket (which someone had given her) and it was badly stitched together, kept coming apart....what a pain.
So, go for it, do it up good!