It may be easier to hold the needles if you keep the RS on the outside when knitting in the round and it may make some of the instructions easiert to follow, especially as the yoke narrows. From the way the parts are placed on the needle it sounds like you're starting at the join between the back and the left sleeve which is a fine place to join.
Count forward from the pattern on the back to see if you line up correctly over the sleeves and with the front pattern. If the pattern doesn't exactly match up, you can decrease or increase sts to make the front, back and sleeves align.
Can you post a pattern link?