Feeling pessimistic

I received my doppler in the mail 5 days ago and have yet to find my babies heart beat. I'm 12 weeks tomorrow. Everything was fine at the 8.5 week sonogram but a lot can change. I'm a little on the bigger side (14/16) and I have a retroverted uterus. I'm hoping maybe that's a reason for not finding it. I'm terrified of a missed miscarriage when I go in the 15th. Now I don't want to announce this week and I need maternity clothes but I feel like if I go buy them, I'll find out I miscarried on the 15th. I know I'm being ridiculous. I just don't want to go through another miscarriage.