When I don’t eat for a day or more I get this sharp pain at the bottom of my throat/neck when breathing whilst walking

I’m 18 years old Female Only medical condition I rlly have is scoliosis I don’t take any medication whenever I don’t eat for over a day I get this pain like it starts off slight then it gets kinda sharp at the bottom on my throat where my collarbones meet. And it always comes on when I’m walking and I haven’t eaten, when I sit down it goes away within a minute. I had a chest infection two years ago now and I didn’t eat for 4 days because it was really bad, and I ended up having this pain for a few weeks and I went to hospital and had an xray and ECG and it was all fine. I’m starting to think that I had it for weeks because I didn’t eat for the 4 days straight, it all started for the first time when I got that chest infection. And it ONLY comes on when I don’t eat and walk for about 5 minutes, what is this?