You have an Opuntia Monacantha Variegata:). It's an opuntia so it could always take more sun. Your plant looks pretty healthy I wouldn't worry to much. It's flopping over like that most likely because it needs more sun.If you could find a sunnier spot your little friend wouldn't mind. I would get a different pot because whenever I use that type of pot the holes always get clogged up. A pot with little or zero drainage is a death trap for cactus. Just get a cheap terra cotta pot. If you wanna go bigger don't go more than an inch bigger. Also make sure you use fast draining cactus mix. Preferably without peat and also mix with pumice or perlite. A mix of 50% cactus soil and 50% pumice or perlite. Goodluck:)

ps- Rotate your cactus so it can get the sun evenly:).

It looks pretty darn good, so whatever you are doing keep doing it.

Only to add to Kara's good comments, if you can find pumice use that instead of perlite. Pumice is much heavier, and with a tall plant, the added weight of the pumice helps the pot stay upright. Tall plants need heavy pots so they don't fall over.

Any chance it was fertilized just before the growth spurt, or that you used a soil that already had fertilizer in it? Nitrogen can cause rapid growth that is so thin that a plant can't support the weight of it.

I'm sure you know most cacti and succulents need very little, if any added fertilizer, but you might not have realized that some soil already contains enough to cause a growth spurt.

Being peed on by a cat or dog can often cause it too. There's lots of nitrogen in urine, so a little causes rapid growth and too much causes burn.

Thank you all for your help!! I feel so much better! I'm going to rotate it more often now in hopes that it'll straighten out. I'm going to go to the store and get a terra cotta pot as soon as I can, I want this guy to be with me for a long time! <3