What should a pregnant woman do if her discharges increase and she suspects her ablution has been invalidated during circumambulation (tawaf) or when the time for prayer begins?

If you perform ablution (Wudu') before entering the courtyard of the Haram, you may perform circumambulation (Tawaf) and prayer with that ablution. The general principle is that purity (Taharah) remains until you are certain it has been nullified. Doubt or the possibility of something having exited does not count. If you find discharge that nullifies ablution after you have finished, then the event is added to the time it was observed, and the nullification of ablution is not ruled except from the moment the discharge was seen.