I used to have the same problem with my forehand.. In my opinion, you really have two options:
1) Go out and practice, practice, practice, practice, practice and then practice some more. Have someone toss the ball to your backhand, then hit to your backhand, then serve to your backhand.. Get a bucket of balls, have someone stand at the service line and just keep hitting them to your backhand. Start off just trying to get it back, then slowly work up to the end of the bucket where you're hitting down the line and cross court.
2) Don't think about it. Practicing will just put more focus on your backhand and just make the thoughts about it more prevolant in your mind. If you practice it, later when you play you'll be thinking about your practice, and then even more worried about it. It sounds like a mental problem, so just try to not think about it, think about the basics: eyes on the ball, swing through. Move your feet.
It really depends on your style. If you're one that can hit the courts for hours at a time practicing, try option number one. Go back to basics that way, with easy shots and getting back in the habit of hitting. Or, if you like match play, try option two and just try not worry about it. You know how to hit the backhand, you've hit in the past, so why should now be any different? The answer: because you think it's different. But it isn't, it's still you hitting the same shot. So, with option two, go back to the basics in match play; just get the backhand back in play, wait for your big forehand or for the error, and take the backhand winner when it's lined up for you.
Also, with option two, try playing someone you know you can't beat! Especially someone who hits harder than you.. It gives you less time to think about your shots, rely more on instincts, and if they're a lot better you just go for more and relax. One of the best matches I ever played was against a kid from a private school who had played all his life, I lost 6-1 6-1 but I was going for my shots, and hit some HUGE backhands and even forehands. I got killed, but in reality I was in every point, and considering I had only been playing 4 years at a public school, and this kid had 10+ years at a private one.. it should've been much worse
For me, I used to miss my forehand by a lot
my senior year in high school. My backhand I can hit a winner from anywhere on the court. My junior year, my forehand was working too.. But then I switched up rackets my senior year, changed strings, and when I tried to get better, I actually went backward. I used to put way too much spin on my forehand and it would sometimes bounce before it even reached the net
. Bottom line, I went 2-8 the first part of my season, then rebounded mid-season to lose only one match the rest of the year before the year-end tournament, where I placed third and moved onto State Qualifiers. I went more with option number two, I just went back to my basics and how I played my sophomore year: just getting my freohand in and waiting for the big backhand. After a while, the confidence came back.
I'm not exaggerating when I say I had exactly the same problem with my forehand. It was almost embarassing to have such a strong, solid backhand, and then have my forehand hit the back fence or not even make the net
. I would line up, bring my arm back, and when I went to swing it just mentally felt wrong
. I would go way too over the top and it would bounce ten feet in front of me, or it would fly off my racket.
Anyway, that's my rant for the day
. Best of luck to you
. You have to game, you still know how to play, so just get back in the habit of it. Move your feet, relax, wait on the ball, keep your eyes on it, and if worse comes to worst: push through the ball a couple times early on in the point before you start swinging again.