Your drain could be plugged up with hair, soap scum,etc. Home Depot has a product to clear the drain. I can't remember the name of it but it the hd people will know

I don't recommend using draino, if you're not careful it will ruin the finish on your drain and if you have an older home with cast iron it could damage your pipes. I always use a tool called zipit, you stick it down the drain and it has barbs on the side that will snag the hair and remove it from your drain. You may have to do this a couple of time to remove all the hair but it's worth it knowing you have a clear drain.

Is your drain slow? I can't tell if its clogged from out here in California...but the ticking sound? Do you have a vinyl shower pan? And is your drain piping ABS...black plastic? A hot shower can cause plastic to expand...and contract as it cools. ID look to see if any of these parts are contacting a dissimilar material. The vinyl pan not adhered to the mortar base below or the ABS touching the wood subfloor as it comes out of the pan. A leak is pretty easy to detect. If there is water dripping in the crawl space or basement after your shower, or the ceiling of the room below the shower has a big wet spot on it...something is leaking. Call you plumber!