I am working on a dresden plate quilt and wanted to add sashing between the blocks to make the quilt a little larger and to break up the design a little. (Making king size)

The blocks are 22" square and I made 5 rows of 4 blocks with 6" sashing between (anything narrower looks puny). And laying it out my rows all line up, but when I try to add my sashing between the long rows i created i am ending up several inches off at the bottom. I have only tried sewing 2 of the rows together so not sure if the rest will line up or not, but with the size i would rather not rip out to much unless necessary.

Can't see a picture.

Here is a picture:

Are you sewing your rows across or vertical?

A bigger picture (showing more of the quilt) would be helpful.

Are you measuring and pinning the sashing to the quilt top?

Or did you just put right sides together, match at the starting point, and sew to the end?
'Cause that is going to cause a multitude of problems.

I'll be watching for the additional pictures.

I did the sashing vertical rows first as the quilt is 4 blocks wide. Now attempting the horizontal rowes to put the 5 rows of blocks together. I'm trying to do the horizontal rows as solid long strips instead of making corner pieces.

you must press your row, then measure it for the horizontal sashing strip.
then lay it on the row matching the ends, and pin. then match the center and pin. it necessary (if long row) pin in between also. pins help and don't use an extremely tight stitch.
also use a foot that allows the fabric to move easily under the foot.
this one shows corner stones-
http://www.synthcom.com/~val/Quilts/Tutorials/AddingSashing.html

As Nativetexan said, you have to pin and pin.

Can you post a bigger picture so we can see the whole thing?

Looks like a walking foot is in order. I always get uneven seams without my walking foot no matter how careful I am or how much I pin.