Late 2013 MacBook Pro 15" Retina makes a clicking sound

I searched this forum and the internet for the problem but with no success. I just bought a macbook pro late 2013 model a month ago and there's this annoying clicking sound, specially when I use it on my lap and at a certain angle (when I am in bed and use it in a 45 degree angle or so), but sometimes also when its in my desk. It comes from the left side but I couldnt tell what triggers it. Sometimes it clicks at a rate for a while and then stops, but mostly it clicks when I open something (like a web page or an ap). Sometimes it clicks exactly when a page loads, like the images or video or whatever. The clicking sound is not too loud, but it worries me.

Some people have reported a similar clicking but related to sudden motion sensor (which my macbook is not supposed to have since it has SSD). Other people have reported that the screws or trackpad were the source. It comes from hardware inside and I checked with the speakers on mute too to make sure. I also tried downloading an app to control the fan and putting it at maximum to see if the fans were the problem but I didnt notice a direct link. I know that somehow it is related with what I do in terms of software (as I said opening something), but not always!!

Does anyone have any idea of what it might be? What should I do?