Actually it is very easy to find out if you snore or not, but there is a catch also.
How to find out if you snore?
Ask Your Partner If You Snore
Snoring when living with others:
Ask your parents if you snore
Ask your partner / girlfriend / boyfriend
Ask your friends (if you ever slept over in someone’s house)
Ask your neighbours (if you have thin walls)
Snoring when alone:
Record the night with a voice recorder
Record the night with a web cam
Record the night with a camera
Go high tech and use a sound activated voice recorder to catch snoring
Now about that catch, which I mentioned: It is very much possible that you could snore when sleeping in one position and not snore when sleeping in another position, so it could very well be that you catch nothing by recording, but you actually snore another day when you sleep on your back for example. So ideally, you want to record yourself a number of nights to have a higher chance of knowing the truth.