The age of a pegnancy is calculated from the first day of your last period. You should be around 39 days pregnant at the time of this post. Accordingly, you probably conceived sometime during the first 10 days of July. But, because you are saying that you haven’t had sex since the middle of JUNE then there are 2 possibilities:
1. Perhaps your last period wasn’t on the 20th of June but was earlier and went unnoticed. This scenario indicates that the bleeding on the 20th of June wasn’t a period... but another form of vaginal bleeding. Such vaginal bleedings can occur during a pregnancy on the day of an expected period during the first months of pregnancy. The vaginal bleeding can cause confusion and a miscalculation in the age of a pregnancy. 2. The second possibility is that you had sex and conceived in the first half of July.