Go to my dentist every six months, will my dentist be able to catch early signs before it turns into periodontal disease?

U can see it sooner!: While everyone talks about bleeding gums being the first sign of gum disease, few realize that most periodontal disease occurs "between the teeth". So if you are tooth brushing and your gums don't bleed, you are not "out of the woods" try flossing. If you gums bleed, you may have gum issues. Healthy gums like healthy hand skin doesn't normally bleed from light stimulation!

Probing: The way to detect periodontis is by probing and by looking for bone loss on x-rays. Ask your dentist how often he does this and what the results are. How often you have x-rays is based on your dental history.

Most likely: If they are taking all those little measurements around each tooth, then yes, they will most likely catch it. Working with the human body though, nothing is always perfect.