Wax begonia

i bought this plant in my early stage as a gardener. i bought so many nice flowers that time that i took it for granted and neglected it. i even failed to appreciate its beauty. i guess i was very obsessed with my roses that time. i hanged it at my orchid house which is at the corner i rarely go to since orchids do not need frequent attention. and spent my time at the garden with the rest of the plants. after a month it started to look sick. its leaves started to rot. a state i do not like to see at all. i was clueless as to how to take care of it. i forgot its name hence i couldn't do any research on how to care for it. until i bought a book on decorative plants.. and i recognized from the picture and relocated it to the front porch where i always hang out and started to water it religiously. the book said i should water it very often and not to give direct sunlight. after a few days it looks healthy again. however for the last few days it started to look sick again. the leaves are rotting. a landscaper came to our house to create a fish pond. we hired him to do landscaping for our house as well because we got so impressed with his previous work. i asked him what is wrong with my wax begonia and he said it should be transplanted to a bigger pot. i just hope he is right.

summary on how to take care of wax begonia aka fibrous begonia:
water: moderately but frequently in full sun.
sun: prefers part sun but can tolerate reasonable light.
soil: moist
growing:a great edging or border plant.