I've been having constant pain in my upper left ribs, right under my bra. This is sometimes accompanied by pain across my diaphragm and nausea.?

See your doctor. It's my job to think, "what's the most serious thing this could be?" and with these symptoms, it could be heart disease. Women's heart disease symptoms can be hard to sort out; they're different from the "elephant on the chest" that men describe. I've had women in my practice experience forearm pain, jaw pain, or even the sensation of a bra that's too tight. It may be your gall bladder, but check!