Congrats on the BFP! Pregnancy symptoms can come and go. A good friend of mine is 16 weeks pregnant and she told me that her breasts never really got that sore. She mentioned they felt a little heavier, but the soreness went away not long after she got her BFP. At least for her, all is well. Of course if you have concerns, speak with your doctor about them. I'm sure everything is fine. Once again, congrats!
I to had 2 m/c and i'm scared too. It's not easy, we are always with the spirit ready to leave. Keep faith that everything will go well. Good luck and happy pregnancy.