I found the first week to be so horrible that words can hardly express. I ended up writing a tome almost a year ago detailing each day for the first week, that I posted on this forum at day 7. I felt such relief and an outlet for my grief when I googled and found this place back then. I'm still not sure how I would've coped without lightning-strike....
The weeks following are still horrible but you just start to gain traction with your sanity and emotions.
The months following are like waves in the ocean. Some days are calm and others are stormy, like 50 footers that threaten to consume you.
All the while, you miss him. You miss him so very much. You try to go on and live and there are good days and bad. There are a lot of bad days in the first few months.
The overriding, underlying current of your being will be Otis during this time. Otis is such an adorable name

. The memories pop in at unexpected times, and flood in at other times. All the while you will feel a sense of loss and missing him. This is the cruel process we must endure when we lost a best friend; a friend that never judged, that loved unconditionally, and brought joy and love into your heart. The more you loved him, the more it will hurt.
I don't mean too sound so clinical. I'm just giving you my own experience. I lost my boy almost one year ago and I am still so consumed with grief that I've decided I need some professional grief counseling. I'm telling you this because I truly understand the surreal, painful, frustrating,etc ... feeling you are having. I have been through the 7 stages of death a thousand times over now. But I find myself stuck in the Denial one. Even after all this time, part of me refuses to believe he's gone. I just feel him all the time, see him, remember every second of our lives together. I can't seem to let go because he was so powerful, omnipresent and joyous in our lives that I can't/don't want to give him up.
Otis will be with you a for some time still. I take comfort in believing that our beloved's spirits stick around a while until we're readly to let go and move on without them. They were always with us in our times of need in life, and spiritually, I believe they continue in death, sitting at our feet, waiting for a good scratch behind the ears. He will be there until you are ready to say goodbye (you will feel him, see a glimmer of him sometimes) and even when that day of saying goodbye comes, he will be in your memories to keep fresh so you can meet on the rainbow bridge and pick up where you left off.
My heavy heart goes out to you. I cry with you. I am angry as you are. I am sad with you. I empathasize so deeply. You have a long journey ahead of you and I will be thinking of you and Otis, focusing my thought energy towards You, and your healing and your broken heart.
Take care and be sure to talk to others so as to not feel so alone in your grief. If you have no one who understands, you always have this place. We all understand (too much).