
I would definitely complain and I'm glad you're going to too.
We all scare ourselves silly with medical worries at one time or another but that's beside the point. Your former GP did nothing to alleviate your REAL medical problems and that in itself is an outrage.
Whether you take it beyond an initial complaint is up to you but at least you have drawn attention to this idiot's negligence; hopefully no one else will suffer because of his incompetence.
Your new GP sounds like a top bloke. He, nor his practice will blacklist you. He has no reason to.
I hope you get everything sorted to your satisfaction v. soon. x