What happens if i only take 18 yasmin pills instead of 21? will i still get my period?

I'm on Yaz so I'll try to help as much as I can. What I would do is continue to take your pills normally and skip over the placebos and start a new pack. This will push your period back to the end of the pack and if you're lucky and have been taking them for a while you won't suffer any breakthrough bleeding or anything. I successfully pushed my period back a cycle with Yaz, women do it a lot for a special event. Ask your doctor if you're unsure. Congratulations on getting married and good luck!