Hi all, Happiest 2019!

So the last 3 days I have experienced an unfamiliar pain in my right side breast. It feels like a mixture of heartburn and something heavy sitting on my chest and seems to get worse at night. I have brushed it off as I am on vacation but am starting to worry...has anyone else felt this similar pain?

I am very in tune with how my body feels but this just has not happened before. I am eating like I normally do, a healthy vegan diet and I barely drink. I am expected to get my period this coming Saturday.

Any idea what this could be?

Have a beautiful day!