Anxiety due to miscarriage

Hi all, I had a miscarriage last year at 7 weeks. I'm now 15 and 4 days and I am so nervous of another miscarriage! Even though everything has been fine this time, I don't 'feel' pregnant, I don't have a bump and just feel bigger. There's no flutters, nothing to tell me I'm pregnant!! I've had my 12 week scan and everything was good then we had a midwife appointment and heard the heartbeat. My midwife says she thinks the placenta is in the front cos of all the noise when trying to find a heartbeat and I think this normally means the bump is smaller? Can anyone give me advice how to calm down and stop worrying all the time?! I'm upset cos I feel like I can't enjoy the pregnancy I was so hoping to have!! X