hello Samira ,
Relax urself ,dont be confused , lower abdominal pain
,with some free fluid as told by ur doctor during check up may be due to infection which do occur often in pregnancy
.u are already being prescribed with medicine and foetal support. since ur pain has subsided and ur cervical length is normal so need not worry ,just relax, take plenty of fluids and complete ur treament.do meet ur gynec if it continues.