Put two poles on top of the jump pole at an angle so they are pointing to the middle. This will lead him in to the centre
You should try to keep using your legs, but in a more efficient way. Like not using your legs all the time, but only when your horse tries to avoid the jumps etc. If you use them all the time, the horse won't notice that he is behaving badly and won't understand what you want him to do, he will get confused.
Usually, this happens when we are trotting into the jump. His pace is fast enough, he is just so hard to get straight! I look straight ahead the line, but he always does this. It’s making me so frustrated. Also he just got a vet check and he is totally fine. No pain.