Pressure in upper abdomen, lowered appetite, shortness of breath when I eat

[sickofsickness]

For the past couple of days I've been noticing this pressure in my upper abdomen, right between the lower part of my ribs. No pain really, but it feels like something heavy is sitting on my abdomen and I still find myself clutching it. I've also noticed that when I eat, I find myself having to catch my breath. I experience random periods during the day when I have to catch my breath, which is a problem in itself, but it seems to be worse when I eat. Because of this, I have less desire to eat and feel slightly nauseous whenever I do so.

I'm also on my period right now (sorry for the TMI), but I've never experienced this particular feeling before. I'm worried that what I'm feeling is some sort of tumor or an aneurysm. Any advice?