You shouldn't rely on BMI. BMI is just a reference and doesn't tell you anything straight out, because it's just a math equation and it doesn't have eyes, it doesn't have a degree in anything etc. BMI is not that reliable!
Also, I couldn't do pushups either, then I weight trained! Now I can! I don't lie to you guys - I know what I'm talking about because this is all personal experience. Don't doubt me