What do you think about PDA?

Me and my girlfriend are pretty far in our relationship. (Emotionialy, ually, etc.) We will kiss infront of people and holdhands when we are together. But i sometimes think that she is uncomfortable with this. Is she embarrased of me or does she just not want the attention of people on us? and i really dont want some 16 year old punk to be answering. haha thank you!