I hope I can help ease your worry. as a mom to 2 children and had 1 m/c... I can sympathize with your worry. but be assured it is normal for symptoms to come and go. if you are really worried, call your dr. see if they can get you in for an early u/s to ease your worry.
by the way, being pregnant, you are allowed to worry whether you feel you have a reason or not.
I am so very sorry for your friend, as I said I did lose a baby of my own, so lots of hugs and prayers to your friend. but don't let that worry you more, and thinking it may happen to you...
call your dr. that is what they are there for!
Best of luck!
D.