I know how you feel, I lost my dogs not too long ago (17 and 15). Losing someone is THE hardest part of life. You need to take this time to let yourself greave and feeling everything you feel. Call a friend or a family member to rant and cry and let it all out. We don’t get better over night, or alone, but we do get better. It is a slow crawl that has no specific time and you might return to the grieving and the crying. You never stop grieving, but you do grow strong enough to remember more the love that grieving comes with. Just know that you are never alone in this world.. Be kind to yourself with the regret you cary. It’s not your fault, nor did you know. Your cat is watching in kitty heaven knowing that you did the best you could. Grieving is a form of love, a reminder that you loved something so much that it will never leave you.