I would recommend that you get your stomach working correctly because that is most likely the cause of your SIBO. Your stomach is not producing sufficient acid which means the acid is not sterilising your small intestine. It might be worth doing a stomach acid test with sodium bicarb.

It might be worth adding culinary herbs such as cinnamon, basil, thyme etc and maybe a little sage but be careful with this if you have been taking oregano for a long time as it might of affected your liver function. Adding these to your diet should help destroy the bacteria. They should be gentler than essential oils.

Cinnamon bark essential oil might be worth trying as a last resort but it can be very difficult to take as it is very strong.