The roots are what support the pads, so the issue starts with the roots.....if you are sure the roots are healthy and intact then the plant is probably fine, support the stem with rocks of something else. Maybe checking the roots is in order?

Thanks SO much! How do I check the roots? :)

The soil is the same soil I purchased it with. It's a sandy mixture. I haven't repotted it ever. I've had it for about 5 months now.

The soil looks like it is Native soil from somewhere. Sandy soil often is not good cactus soil. You might want to add an equal part grit , as in Perlite , or Pumice to the mix and put the cladode (pad) deeper in and put two wood skewers on either side to help hold it up till the roots get a better grip and put the pot in the sun. I think the dirt has compacted down. You can see where the dirt line used to be, and the level of dirt in the pot looks very low. That means that the drainage in the soil is getting much less and the air in the dirt is dissapearing. NOT GOOD. When you water it , how long does it take for the water to recede? This opuntia is more water tolerant than others but it still needs drainage.. Opuntia type plants can deal with more root space than other cactus. They like it. I would suggest a bigger clay pot. If you do take the plant out let it sit for a couple of days before you re plant it and then DO NOT WATER IT for 3 -7 days. The roots need to callus ( form a scab ) from any cuts or bruising. Then give it GOOD sun.

Do you know what type of Opuntia that it is. It could be Nopalea cochenillifera. Synonym is Opuntia cochenillifera. Someone( a splitter) has been messing with those scientific names. It is hardy to about 20F maybe a little lower. Where do you live. Not to be nosey. This is a big cactus . It will be happiest outside . I have seen these 14' and big around as an SUV. This opuntia will be much happier in the ground. I have seen them in pots and I think that they keep trimming pads off of it to eat them , making it branch and stay small and IN FULL SUN. I am not sure how they grow them in pots. The first pot maybe had pads taken off and rooted by its parent.

Included some photos of this cactus growing in pots in FULL sun outdoors in Mexico. Outdoors all year long in full strong sun.. and a photo of the monster this can become. This is naturally a thin and floppy variety. If it is in reduced sun , it can not support itself because of the stretching out (etiolation). This is not a cactus for a living-room collection up north unless you have a large space and great lights.

The other variety that it could be is Opuntia ficus-indicus, another large one hardy to 15F maybe. Mine bit the dust at above that..

Cocheneal Nopal

More info from Eat the weeds

Thanks for the soil tip! I am not sure of the exact name, it was a gift.

I live in Texas, so the sun/ tempature issue isn't a problem. It will live outside in a pot, although it can be a larger one if needed, until we move to a space with a garden where this guy can spread out.

I live north of Dripping Springs ( West of Weird) and a 14' one died in the bad freeze of 2010. I think it got to 13F quickly followed by a 16F front. The double whammy was too much. There was an 8' one at my doctors lot in Austin and it die in that freeze too.

North of Dripping Springs, and West of Weird. ;-)

LOL, can't be too exact on the web. I want to correct something. Sandy as is sugar sand is not good in POTS. Grittier sand is better.. I do not know why one thing will cause drainage in one situation and do the reverse in another situation. I do know that people with a lot more knowledge and multiple ag degrees that are growers and breeders in Ca. say this. But all these commercial succulent soil people think that by adding sugar sand to peat moss, one makes cactus soil. There is a big disagreement of techniques here. I do know that commercial cactus soil has killed several potted plants of mine before I saw the light.