when you first wake up in the morning and feel this pain...describe it. does it feel like a cramp, or pressure, or burning or even something else? and what happens if you drink a glass of water and remain upright?...does the pain diminish at all, even for a short while? or if you take an antacid like maalox, tums or rolaids does that help?
I wouldnt latch on to gerd as a diagnosis without getting your doctor on board. it may well be gerd or something very different.
you might want to get some testing to find out for sure. if it were me id ask the doc for some testing, such as, esophageal ph monitoring, to know for sure. although many doctors just jump to write a prescription for H2 antihistamines ( like you can buy otc) or PPIs (proton pump inhibitors) which will turn the quantity of produced stomach acid way down. and then if you note improvement they take that as evidence your pain is acid reflux related.
hang in there, ask questions of your doctor and stick around here for more info from other more experienced members
best of good luck to you