Sarah, I’m so sorry for the loss of your Dallas - and the loss of your mum. I’m glad you’ve come here to share your experience and what you’re feeling; it has really helped me. I lost my Buddy in early March to some similar issues, and also lost my dad a year and a half ago.
Buddy was 2 months away from his 10th birthday, so was considered a “senior,” but until just a few weeks before he passed, he seemed healthy as ever and doing fine. Then he suddenly developed breathing issues, which the vet figured was mild asthma that got a bit more serious - and I started him on medication for that. A couple of days later, his breathing was worse, so we brought him to the emergency vet hospital, figuring it was an asthma attack - and they would administer a feline inhaler, and he’d be OK. But something happened in his carrier on the way to the hospital, and he was basically gone when we arrived. They said it appeared he threw a clot. It floored me. What? How? I felt terribly guilty that I had missed something, or had stressed him so much that it caused this. I had a necropsy performed, and it turned out Buddy had undiagnosed heart disease, fluid buildup in his lungs, and tracheal cancer - even though I had just taken him to the vet for a checkup and x-rays 4 days before he passed. None of these conditions were detected; the only thing they saw was that his trachea was narrower than normal. I’m relating my story (like James & Julie have) to help reassure you that you did everything you could. You didn’t miss anything, cause anything, or do anything wrong. It can be hard for even the best vets to diagnose and treat an animal’s illness, since pets can’t tell us what hurts or how - and since they often hide pain or injury as a survival mechanism, as part of their DNA. Sending you hugs...
Cindy (Buddy’s mama)
My baby Buddy 5/4/10-3/7/20, rescued March 2011 My sweet Mandy 11/27/91-11/2/10, rescued November 1992 My beautiful Barney 4/28/73-9/7/92, adopted May 1973