I got 2 fertility potions but when I went to check they gone

@Ariesss6 I've never used that in the Rewards Store, but I just looked it up and those potions cost 3000 points! Ouch!

• I went in with my Sim and checked on this, as I was going to test if I could have her purchase a potion and upload it to the gallery for you if you wanted it, and I found that when I purchased it there was no potion in her inventory. Then I looked at the item in the store, and it doesn't seem to be a potion, but rather a purchase that increases the likelihood that Sim will have twins (though twins or triplets are not guaranteed). Please see this screenshot:
  
  So... if you purchased that for your Sim, I would assume that the Sim has an ongoing higher likelihood to have twins or triplets?

Here are a few other things you could try:

• My main Sim had never had twins before and I really wanted them for a goal I was doing, so I what I tried was adding the "On Line Key" lot trait to the lot, saving, reentering the lot, then they tried for a baby and it was twins! (Though twins are not guaranteed with that lot trait.) This lot trait comes with the "City Living" pack:
  
• If you own the "Spa Day" pack you can get a 'fertility massage'.
• There are some pregnancy cheats out there you could try, but I'm not sure how well they work currently in the game.
• Keep in mind that you will need at least two open slots in the max of 8 Sims in the household. In other words, if you want to get pregnant with twins, you cannot have more than 6 sims already in the household... and that includes Servos, cats and dogs, and pregnant Sims (and pregnant Cats and Dogs) that have one or more slots already taken up for whatever number of babies they have 'on the way'.

So, anyway... hopefully that means your Sim is more likely now to have twins or triplets if they purchased that in the 'Rewards Store', and I suppose if you want to make it even more likely you could try one or both of the above in combination with it! Good luck, and I'd love to hear how it went and see pics of your twins! 🙌 Here's a screenshot of mine (that I mentioned above):