Is my sternal pain serious and should I see a doctor about it?

I get intense pain where my sternum is probably once every week or two. I didn't think it was that much of a problem at first because I already suffer from acid reflux and thought it was just that. But the pain seems to be getting worse and worse and I've actually started to feel like I'm going to be sick when it starts. I also really struggle to breathe with it and I'm scared it could be serious. I'm only 15 years old but I'm prone to panic/anxiety attacks and my mum has had lots of issues with her heart in the past. We have a long family history of heart attacks and I'm absolutely paranoid I could have one. I know it's unlikely since I'm young but this pain in my sternum is really worrying me! I can't sit or lie down when it comes because if I do it feels like my heart's going to literally explode.

I'm scared out of my mind. Does anyone know if this is serious or not? :(