Is it normal to miss a period whilst on yaz (drospirenone and ethinyl estradiol)?

Maybe. It is not uncommon with pills like Yaz (drospirenone and ethinyl estradiol) to have a very light or absent period. Yaz (drospirenone and ethinyl estradiol) only has 4 days of placebo so this is common. If unsure you can always do a pregnancy test.