Weird Left Side Pain Continuing for Months

I'm not sure if this is the right group for this, so please send me to another group if that is the case.

So, I have been having a lot of pain all over the left side of my abdomen for several months. The pain has typically started in the same specific place just under my shoulder blade each time and has subsequently radiated to the left side of my chest, down my left arm and into my back, side and upper stomach area on the left side. Lately, the pain has also tended to start in a specific area on my left abdomen that is sort of just underneath my bottom few ribs and on my left flank. That puts it above my belly button height wise. The pain starts and stays there and sort of radiates out closer to the center of my stomach, up into my back and shoulder and into my chest and arm.

I would describe this pain as dull and kind of like "warm" for lack of a better word. At some points, it feels a little crampy, almost like a side stitch. Sometimes - especially if I lie down (esp. on the left side) or have acid reflux due to eating fatty food - the pain gets sharper and more intense, to the point of being very painful and distracting. It also gets worse if I hold up my left arm, i.e. to write (left-handed) or hold the steering wheel while driving. It usually gets a little better but not totally better if I take off my bra and it can be made worse by pressing on the hurt areas. Typically, it comes and goes and usually lasts for hours to days when it comes. It has been going on for probably 5 or 6 months and steadily getting worse.

I've been to a cardiologist about this and gotten my heart checked out pretty thoroughly (MRI, echo, repeated EKGs) around the time these problems started. My heart isn't perfectly normal due to the previous heart defect and surgery, but it is healthy and I don't need any drugs/additional surgery/etc. Essentially my heart is just like it has always been throughout my life, since before these problems started.

I know I have some sort of GI issue like a tear or ulcer and am on proton pump inhibitors to reduce my acid reflux. I don't know that this fully explains my pain, however, because the pain in my chest and shoulder started before I noticed the acid reflux. I don't know if it could explain why the pain is localized on the left side of my abdomen. The acid reflux and this pain kind of go together though.

I was considering that it could be a kidney infection, since I've been going to the bathroom a lot and that could indicate a UTI. The frequent urination has been a feature in my life for a few years but I have tested negative for UTIs repeatedly despite this. I did have a UTI about 6-7 months ago, got treated with antibiotics and got tested to verify that the UTI was gone but maybe it came back. I'm not sure if the pain I'm experiencing is severe enough the be a kidney infection though. A few other possibilities are an issue with my spleen, an issue with my pancreas, a displaced rib or diverticulitis. I'm not sure why I would have any of these conditions because I'm pretty healthy, pretty active and am young with no personal history of health problems besides my heart. The one that makes the most sense is a displaced rib since I mountain bike and have had a number of crashes where this could have happened, but my last bike crash happened over 6 months before these symptoms appeared.

What might cause this? I'm seeing my GI doc again soon and getting an endoscopy but should I be getting other tests done? I got a blood test to check for anemia and thyroid issues a couple days ago as well, since I've been fatigued, having occasional heart palpitations and generally feeling unwell. Would those tests show if any of the issues mentioned above were present? Thanks.