Help with pad cactus growth????

I've had a sizable pad cactus for a few years, it's about 1.5 - 2 foot at it's tallest shoot and it was bought for me as a present. I love cacti and own quite a few. The pad cactus gets alot of new growth each year, but instead of growing more round/oval, the new growth always grows long and tall and often then cannot support it's own weight especially if that then gets new growth on it. Is it the conditions? It gets a nice amount of light and seems to like the room it's in, I don't over or under water it. Can anyone help?