I'm so sorry to hear that. It's very draining when someone you care about dies. Let yourself grieve, don't let anyone else tell you otherwise. I made that mistake recently, letting someone I thought cared about me tell me to get over it, move on with my life and go back to work the day after my Grandma died. If you ever need to chat to someone, just e-mail me (I'm sure my address is on my profile!). I may not reply immediately due to the move but I promise I will reply if you contact me.
I'm sure you shared some really special times with that friend. Remember those and they'll never be gone.