Nowadays the rupturing of a silicone gel implant is getting less frequent, they still can leak.
If they do, you will not notice it right away. They only way to do it is the recommended yearly MRI (min. $2000) or watch out for other symptoms that make you suspicious since they were not present before your surgery.
Aches, tiredness, fibromyalgia, rheumatologic problems or basically anything unusual.
Unfortunately, the unusual "not feeling well" mood can happen years after your surgery so it is harder to relate to your breast augmentation surgery.