Scared & very unwell. Stomach cancer?

Hi. I’m currently experiencing some really odd symptoms. Started with passing out back in October,then noticed my appetite was really poor. Felt full quickly. I’ve had post nasal drip for years on my left side only and sometimes rib pain on the left side. I put it down to the PND making my stomach sore or even it getting on my chest. So roll on 6 years and the odd symptoms started. 

I’ve no appetite but have tried to keep eating, then noticed that every time I would eat, I’d feel really dizzy. Then pain in left rib got worse. Breathlessness too and heart palpitations. I’ve been to A&E twice and they said it was Costochondritis. 

Last week I passed out again and went back to the doctors. There she felt my stomach and said that it feels hard. I’ve also had Diarrhea and have lost 8 pounds in the last 4 weeks. So she has sent me for an urgent endoscopy. I’m awaiting to hear when my appointment will be. But meantime my symptoms are getting worse. I can no longer eat anything without feeling extreme pain that radiates to my back. Also the dizziness. And the nausea that come with it too. I’m scared to eat anything larger than a couple of mouthfuls, because if I do, the burning sensation in my chest knocks me for six. My heart races and I feel like I’m going to have a heart attack. I have so many dark thoughts. I’ve been a smoker for 25 years and I have a 7 year old daughter. I can’t bare all of this and the waiting. I don’t feel well enough to leave the house it’s that bad. 

Night sweats and lump under left armpit too! Feel really out of it and nothing seems to help  

Any advice out there would be welcome with open arms. My chest, stomach and back hurt so much.