It’s great that you use condoms, but unfortunately that doesn’t mean you’re definitely safe. If the condom is past its expiry date (yes they have one) then it will start to breakdown and can prove ineffective against STIs and preventing pregnancy for that matter! There are other reasons why condoms may not always work for example if you use an oil based lubricant such as Vaseline or massage oils they may cause the latex to disintegrate so whilst using a condom is a very good idea they’re not foolproof and you should still get regular STI tests to be absolutely safe.