Is it possible those round black objects were things he'd ingested and thrown up? Dogs can be very stoic about pain, not showing many indications till it gets pretty bad. Your golden is showing signs of pain: not interested in food or walks and walking around gingerly are danger signals that something serious is going on. It could be something like an intestinal blockage or something irritating his stomach.
If it were me, NesTea, I'd be bringing my dog in to the vet today.
I hope he's okay!
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."