My Dog Passed Away Recently After 9 Years Of Having

My dog passed away recently after 9 years of having her, since she's passed away i feel like I'm sinking in emotions I can't control, I'll have nightmares, difficulty breathing when I get too upset about it, I feel myself becoming moody and hard to handle yet I can't control it, it's like she was the only thing holding me together and now I'm losing control. What can I do, I feel like it's affecting my health as it's making me unstable and half the time I can't even bring myself to eat.