I Can’t Get Over Losing My Cat

driving my family mad and just can’t help it! My four year old cat died recently and I’m distraught. I blame myself for not noticing her swollen tummy and not taking her to a vet sooner, so she had to be put down. I had my previous cat for 15 years and did not feel like this when she passed. How do I get over this? My son suggested getting a dog, but that’s only because he wants one. I’m bursting into tears at least once a day, I miss her so much.