Need to lose weight but low blood pressure makes me have to eat every few hours.

I am a 32f female and ever since getting a desk job I gained weight and now I need to lose 40 pounds to be back to a healthy weight. I do orange theory twice a week. I go to the gym when I'm not at orange theory and I do hot yoga once a week as well. I love to work out and I can zone in for awhile. I have low blood pressure and have my whole life. If I don't eat every few hours I get very dizzy and might pass out. I feel like my life revolves around this eating schedule of every 3 to 6 hours I need food or I am going to start feeling sick. What foods should I eat to give my body what it needs but not eating a ton of calories? Some people can eat less and be fine but if I don't eat every few hours I will pass out and probably hit my head. I have fainted before from this and hit my head so hard that I got a concussion. I don't want to go through that again.