I think I have a virus or some form of malware on my macbook, is this possible?

When I opened one browser page of safari, it failed to load and instead went on to continuously open page after page of safari windows all of which failed to load. Eventually I was forced to hold down the power button to just stop the whole thing from crashing. I am not sure if this means I have managed to aquire something like a virus or trojan, considering I surf the internet very carefully. Please help!