Nausea, heartburn, indigestion..

For the last couple of months I have been frequently nauseous. I'm getting so sick of it, literally, I need to get to the bottom of it. At first I thought it was dehydration and yes drinking a large glass of water with a bit of lemon juice in it, every morning seems to be helping somewhat. Also coffee seems to agravate it. So I've been avoiding coffee and drinking more water but everytime I am walking outside I feel like im going to vom everywhere. Maybe it's lack of sleep or GERD? But whatever it is I need to fix it.