I usually take my symbicort inhaler at twice 3pm and then 3am. missed it today and took it at 7pm. do i have to take it at 7am now?

Not necessarily...: ...however, why were you told to wake up at 3am? If it is because you are night shift worker, then I understand. But if not, you may consider rotating to a more tolerable schedule, such as 7am and 7pm. But if you want to remain 3pm and 3am, you do not have to wait until 7. Taking Symbicort again within 8 hours won't hurt if done this one time.