Important Update: 12:55 PM
I went to the vet today, as I stated before. Gibson had a routine heartworm test. The test came back negative for heartworm but showed that he has a rare tick-born disease that destroys his blood's platelets. Meaning he could die of internal bleeding if the blood being tested right now comes back as seriously infected. If that is the case, there is nothing the vet can do. If the test comes back normal, that means we may have caught it in time to knock it out with antibiotics. Either way this comes as a hit to the farm.
I could lose him and there's nothing I can do about it.
Important Update: 5:21 PM
Gibson's CBC test came back okay, Good red blood count! The vet explained that he is not in danger now and either he will live with this as a dormant part of his biology or it will come out in a chronic form later, and I should keep an eye on him for lethargy and other symptoms, which could pop up any time but right now I do not have to worry about it. So relieved!