If you are looking to make the right decission then you need to be honest with yourself.
You have been training for only six months, I don't think you have learned enough about your body yet and how it reacts. I learned my biggest lessons two years in to training, I discovered what worked, what didn't, I discovered I could bench press with 20kgs and get more out of it than I could with 140kgs. It's a focus that takes you to a whole new level.
Diet, how many times a day are you eating. What is high protein? For a doctor that would be 100 grams + a day. It's all relevant. How many times are you eating a day, how much do you drink, smoke?
Learn to walk before you can run and you will thank everyone for it later.
If you are doing a 5x5 and no longer getting results, go for isolation now, do a split routine and see if things change. Remember it isn't the weight that counts but the form and focus.
Additionally although you have given your weight, height and age, you have not provided a rough estimate of bodyfat so you could be huge or you could be overweight in terms of fat or you could be athletic.
Do you supplement with anything at the moment?