The Cincinnati Reds in 1961 had a pitcher named Jay Hook, who might have been a good pitcher except he didn't trust his stuff. One day he started a game against the Pirates, and they ate him alive, converting every pitch he threw into line-drive extra-base hits. When he was finally removed from the game he returned to the dugout and sat there in a corner, bemoaning the fact that his fast ball had deserted him. He kept saying, over and over, "Without my fast ball I can't pitch". In vain did fellow pitcher Jim Brosnan try to explain to him that you have other pitches to throw and you use them when your fast ball isn't there; he might as well have been talking to the wall. Hook didn't last long in the majors after that.
Now, I don't know exactly what your situation is But I would suggest that one of the people you should talk to is your pitching coach, especially if he knows his stuff. He just might have something to say that would get you back on track. I had a situation like that once, where I was facing a nightmare in which I felt that my stuff wasn't working. I talked to my pitching coach, and before I knew it he introduced me to a strategy I had no idea he knew anything about. It didn't take long before we hit the focal point of our investigation---I hadn't even known it, but I was uncertain about my ability to pitch in tight situations with less than my best stuff. In about an hour he knocked my whole problem out of commission and restored my confidence, gave me more support and reassurance than I had ever imagined, and demolished any anxieties I might have had. And the next day I went out and pitched a two-hit shutout.