Welcome to NP Skaboo and Nelly

I look forward to seeing you around the forum.
Congratulations on your pregnancy Skaboo. Perhaps your LO is sensing that you are out of sorts so is feeling emotional. Pregnancy is tiring stuff, plus with your broken sleep it is no wonder your patience is wearing thin when she is pulling your hair.
At that age I found redirection to be the most useful way to discpline. In your situation I would use my regular voice to say that hurts Mummy and change the situation. If we were standing, I would sit and do something with her. If breastfeeding, I would end the feed even if it is just for a moment. Maybe a quick game of round and round the garden.
Once again, I look forward to getting to know you. You may wish to post in the Getting Acquainted forum so the whole community can welcome you.