Hi,
How are you feeling now?
Is baby doing fine in womb? I think it is just a muscle pull. The muscle involved appears to me as Pectorals Ms.
You would also have probably pulled tendon, hence you are having pain even on slight movement.
It would resolve in few days to weeks.
You should be doing mild exercise of involved part this will help you in faster recovery.
Analgesics should be fine during pregnancy and you should be taking Acetaminophen or Ibuprofen.
Keep me informed if these symptoms does not resolve.
Bye.
This will probably go away in a couple of weeks as it sounds muscular rather than a tendon or ligament. It should be getting better day by day. If it isn't then you should quickly go and see your doc.