When your hair is by your shoulders that is when you need to protect it the most. You should consider doing protective styles and make sure to take care of your ends. Keep them moisturized and healthy. Perhaps oiling your ends after using a moisturizer would be a good option for you as well. Also make sure to keep your hair off of your shoulders for now while growing it out because your clothing could be breaking it off. If you are straightening your hair on a daily basis that will break your hair off as well. Go low or no on the heat. Don't sleep on cotton pillowcases. Invest in a satin or silk pillowcase, you can get a satin one pretty cheap from your local beauty supply store.
My hair is mid back length when straight and collar bone length when curly. It is definitely growing but I seem to only notice when my hair is straight or wet since it shrinks a heck of a lot. I have 3c hair and have been growing it out for about four years. I so badly would love it to be arm pit length when curly, but I know that won't be happening any time soon. I thought I would be happy when I got to collar bone length but I guess the grass will always be greener somewhere else.