Begonia Beginner Help! Sad looking Rex.

smellthedaisies

I got this Begonia Rex around a year ago. It was fine until after I moved a few months ago and it started to drop leaves after they turned brown. It was also repotted just before this. I suspected the soil was quite damp and Ive tried to dry it out but I'm  at a bit of a loss as to how to get this planr going again. It is in regular potting soil and lives near a window but not in full sunlight. I've  attached a picture for reference. Please help my save my plant!