It may be true that your designs sell, but theres more to working in an office than that.
How you get along with others (co-workers, boss, etc.), your morale, your ability to take criticsm, attitude, are all factors that could bring the boss over to you for a little chat.
In many offices I know there may be a good worker but who is such a pain in the ass that they have let him/her go… especially at a lower-mid level postiion where there are no shortages of good designers who can step in with just as good design with a better fit into the company.
Rather than asking yourself “why me?”, “why am i getting picked on?”, why not look to see what you can do to improve?
if you think the job is salvagble, and would like to continue, I’d suggest that a chat with the boss could help.
Tell him you would like to improve your fit with the company and professional personality and ask him for pointers on where you can start and what things to look at. Coming at it this way as a self-initiated critique to improve, your boss will likely be very happy as such motivation.
If you go in an ask “why are you picking on me?”, get ready to pack you bags…
The boss is there to manage and if he feels that you need extra time and pressure then there is likely a reason. I doubt that he just likes picking on you and im sure he has more important things to do than spend his time making you do “frivoluous” changes.
Look inside first before pointing fingers…especially if you are on the bottom of the totem pole with not enough experience to push back.
Either way, if you do decide to leave, I’d still do the same (chat with your boss, ask yourself what you can do to improve, etc.). More than likely, with your attitude that everyone else is wrong and you are right, you will run into the same thing at any other workplace…
R