You need to add an extra word after "were" or "had been" like "there", "here" or a verb (e.g. to come).
Sometimes "if you were" and "if you had been" can be used interchangeably. For example:
"If you were there, the accident wouldn't have happened" means the same as "if you had been there, the accident wouldn't have happened".
"If my cat were alive, I would have taken her with me" means the same as "If my cat had been alive, I would have taken her with me".
I think the difference is "if you were" is a hypothetical situation, meaning "if that were the case, then....". So, you can put either a positive or negative sentence with "if you were".
For example: "If you were here, she wouldn't have done it" OR "if you were here, you must have seen here do it?".
"If you were driving, we wouldn't be in this mess" OR "if you were driving, you would have seen the mess ahead"
Whereas, "if you had been" is stressing that things could have been different if only you had acted differently. It is stressing that you could have changed things (hypothetically). Therefore, a negative sentence usually follows "if you had been". In my opinion "if you had been" sounds more like blaming someone or criticising for what they did by saying that the bad result would not have happened otherwise
For example:
"If you had been here, she wouldn't have done it".
"If you had been driving, we wouldn't be in this mess".
"If you had been more cautious with our money, we would be in Spain right now" (an example with a positive sentence afterward, but it still sounds like it is blaming the other person)