I think you have a clogged drain alright, but what you are doing isn't going to help clear it and is just going to waste your time and money. Chemicals do not work regardless of what the commercials try to convince us. The bladder devices don't work, nor do the hand-powered snakes intended for home owners. It takes a professionally sized and powered auger which is very dangerous for a novice to try to operate. You need to bite the bullet and have a licensed plumber (whose business name does not end in "Rooter") professionally auger the line. I repeat...do not put chemicals in the drain. If you do and then call the plumber, be sure to tell him what you put in, how much, and when. Some chemicals can be very hazardous to anyone working on the drain.