can't find heartbeat, please help

Hi I'm 14 weeks and 2 days and for the past 3 days I haven't been able to find the baby's heartbeat. Please no nasty comments but I was using a phone app which has worked since 10 weeks. I payed for this app and it worked really well. I don't have a Doppler. I've been trying at different times different areas of my stomach before and after eating, everything and I just can't find it and this is unusal! I know it says not to worry etc but I just can't help but worry as it has been 3 days and many attempts. What do I do? I'm so scared