Paranoid or justified, I don't know but why on earth would he blab about that other business in front of DS? If nothing led from it and you have acknowledged it was a stupid mistake and have never given him cause to doubt you, that belongs in the past.
Now the boot's on the other foot and you are troubled and want answers. Was anything else setting off your radar, has he been preoccupied, detached, unresponsive, antagonistic?
If DH was texting her to get you back he's wound you up good and proper.
If she is a good friend to you both she will be wondering what is going on.
and probably egged her H to ring yours, most likely.
All her H knows is what she tells him so if she thinks you've lost the plot, he will only be interested in your DH's side of the story.
Stop texting and FBing for now, concentrate on talking face to face.
Take a deep breath, ring DH, ask him to bring home fish and chips and you can sit, eat and talk. This has all got out of hand, focus on DH and you not your friend, (if she wants you babysitting she can ask you herself but this isn't about babysitting is it).