Vet has no more answers and we don't know what to do...

This is gonna be a lot, 6 weeks worth of information but I really really need some help please.   Beginning of June my dog had pneumonia, took about 3 weeks to get that cleared up...right around that some time, her belly started looking bloated. She started having THE WORST gas I've ever experienced from any animal or human. Not being funny, it would make you nauseous and it was continuous. She also wasn't pooping but once every 2 days and it was way smaller than her normal poops. She would get little fluid pockets behind her front elbows/chest area and then they would go away. Had a 2nd xray done and came back with "Possible heart base mass vs. artifact of cervical positioning.” July 1st, she got stung by a bee on her face around 10pm. By 5am, she vomited almost a gallon of blood with golf ball size clots. Took her to vet immediately. All her test were reran and still all normal. Vet thought we could try treating as ulcers. She started taking Yunnan, carafate, Prilosec and benadryl. She had already taken a round of steroids in there too. Sorry it's a lot to keep up with when and what order everything happened. But after she vomited the blood her stomach was normal again. Started chicken and rice diet at that point which is still continuing. One week later, her stomach started getting big again, vet started steroids again and furosemide. All this is happening while she is continuing to have that horrible gas. I kept telling vet and he finally said to start gas x on this week, Tues. On this Wed, her stomach size changed 3x. Large, normal back to large all in one day. I've continued the gas x but Monday I stopped all other meds. I get up this morning and her stomach was completely normal and now it's 6pm here, it's big again. I was set to schedule euthanasia for tomorrow bc that's what I thought I should do bc nothing was seeming to work but I don't know now. With her stomach going back and forth like that the last 2 days, I'm so unsure now. Right now, all she is taking is gas x 3x a day. She has started pooping normal at least twice per day and eating. She's always been a very lazy dog and she still is, so an energy level change would be almost impossible to notice. But she still gets up and follows me around like she always has. Any ideas what might be going on? All her test have been normal, except what I stated above on her 2nd x-rays. I'm desperate for some insight or something maybe my vet hasn't thought of. I appreciate any feedback. Thank you..!

Hello!  Does your vet know that you are considering euthanasia?  Perhaps they will reccommend a referral to an expert in gastrointestinal disease or seek further advice.  It sounds as though the cause is not known, so there is scope for a specialist to be able to help.  I wonder about an endoscopy to see if something is blocking the outflow route to the stomach for example, or whether a partial GDV etc may be occuring.  How would your vet feel about this?

The vet said he didn't think she was a good candidate for surgery and that if they did get in there and it was bad, we'd have to decide to not wake her up and I can't do that. If I have to let her go, I have to be by her side. She had surgery at 9months old after she ate a blanket and almost died in recovery. She did not do well. She is almost 9 years old now. Back when she vomited all the blood, he did blood panel (normal) ultrasound and pulled some fluid out which wasn't blood. That's when he gave us 3 options-treating as ulcers, surgery (didn't recommend) or euthanasia. We opted for ulcers treatment. The most confusing part for me now is the fluctuation of the bloated belly and deflated belly. I don't understand what would make it go up and down like that. And why after she eats. Would it do that if it was blood or fluid or just if it was air? I really appreciate you taking time to respond.