I'm not a dentist. but I've had almost every dental procedure going.
How do you know it's infected? I'd assume if it was infected, you'd have an abscess and probably be in considerable discomfort and your dentist would have prescribed antibiotics. Is your face swollen and are you in pain.
When you have a root canal, the whole of the root is removed (or at least it should be!!) and then refilled. If it's done correctly, this leaves the tooth dead and you should have no more pain from the tooth.
Going off your statement,
//// I don’t really trust him to be honest ////
..... and the fact that he's done the tooth twice and it's still not right, I'd seriously consider changing your dentist.