I am 7weeks 4days preg my babys i fine,only to find out clot in my uterus?

yestrday i went for my u/s wer i ws told now ur fetus is reponding accordin to ur LMP, coz when last weeki went for my 1st u/s tey told me that i ws 6weeks preg, bt d fetus luks lik 4-5weeks, and the fetal heart beat ws also very weak around 105, bt yestrday evrythng ws f9 wit the fetal heart rate also wich is 145, n doctr said its normal, i was relaxed, but wen doc said u hav a clot in ur uterus bt far from d sac, n itz smal sumthng around 0.9, coz of it from past 1week i am havin brown spotting & mild cramps, so my gynac has gven me injction wich she gave me last week aslo to supprt d uterus wich was weak, she said wit tis injction clot shud dissolve and said to tak complet bedrest, m jus worrried that the clot shud not grow in size n coz any problem in my pregnancy, cud anyone plz tel mee, is this normal, has anyone had any similar problm wit a successful delivery.. please help me out...m having these medication also: ARG 9, naturegest 200mg, & folinext D.