is it possible to go past your draw length and go out of alignment?

Yes, you could draw past your ear or head if you just haul back with your drawing arm and the bow is light enough for you to do it.  If you draw correctly, however, you will draw with your back muscles, such that the path of the draw is more of a J shape rather than a straight line.  The J is formed by your drawing elbow tracing an arc backwards around your spine, and as you complete your draw, you bring your forearm in alignment with the arrow.  Most people hit a wall at this point and can't draw much further if they are using their back muscles correctly.  Some people may be able to overdraw, even when correctly using the back muscles, and have to learn to stop when they reach alignment of the forearm with the arrow.

So how do you know when aligned and when to stop?

Video yourself from behind and above, draw in front of a mirror that is slightly above you and angled down, or have someone stand behind you and look.  Your drawing forearm should be aligned with the arrow at full draw. As I said, for most people, if they are drawing correctly, they won't be able to overdraw the bow.  The bigger problem is not being able to rotate the shoulder back all the way into alignment.  However, there are a few people out there who aren't overbowed and who have the flexibility to overdraw the bow even when drawing correctly.