No, its not just you. WhatsApp appears to be down for everyone, from around 19:00 GMT.
Of course the first conclusion one might jump to is that Facebook messed it up, but given that that deal is still months from closing it is more likely one of their engineers flipped the wrong switch.
Interestingly there has so far been no official response on their website, blog or twitter account.
The service is usually very reliable, so I am sure it will be restored soon.
Update 1:
WhatsApp’s Status Twitter account has now posted an update, saying:
sorry we currently experiencing server issues. we hope to be back up and recovered shortly.
— WhatsApp Status (@wa_status) February 22, 2014
Update 2: 4 hours later and WhatsApp has confirmed the service is back in action again.
WhatsApp service has been restored. We are so sorry for the downtime…
— WhatsApp Status (@wa_status) February 22, 2014
Picture via SirJadeja, thanks Brett for the tip.