Low Blood Pressure

I’m fasting on the morning since 2 weeks. I also continue vinyasa yoga twice a week, and going to work in bike. I’m feeling great with the fast and my energy. The only thing is after I´m doing poses where I have my head down at yoga, I have some pressure drop and I’m feeling dizzy. I always had a low tension in my life. Should I just continue as I’m doing and my body will adjust by himself ? Or should I eat something before yoga ? No problem with the bike . It’ s really only when I have my head down.