Where is my mommy?

I am not really sure where this post will end up.  I am sitting in an empty quiet house, kids are at school, hubby working.  The silence is nice but gives me way to much time to let my brain wander.  Spring break is here, today is the last day of school until the 13th.  My youngest son will be spending time with his father, which is great for him not so great for me.  I am selfish.  I want him all to myself.  I started thinking about him a lot when I was trying to fall asleep last night (1 am this morning).  I have been in my own little world & my boy has been neglected.  I feel like a horrible mother & need to fix this.  In my adult mind I realize that it has only been 2 almost 3 weeks since we lost our little Alvin.  He is 7, 3 weeks is an eternity.  An eternity in which mommy has not been there for him.  I try, I try to do all the normal mom things.  I help with homework, I make dinner (on most nights), his laundry is done but it's the little things that are missing.  I haven't spent any time with him.  I have had little patience & lost my temper with him.  He is the sweetest little boy you could ever meet.  His positivity is something that I should learn from.  I need to be more present physically & emotionally but I can barely keep my emotions together.  At 7 he handles death much better than I do.  He asks questions that I don't really want to answer & some that I do.  I try my best.  The other day he told me that he was sad that his brother died but in the next breath asked me when we could get another baby.  For that, I had no answer.  If it were really that easy.  I want to hide in my room, under all the blankets & cry, but another part of me wants to spend as much time with my children as possible.  I don't want to look back 10 yrs from now & have regrets.  I don't want to make a negative impression on their childhoods.  You know, where they are older & talking about growing up & say "remember those WEEKS or MONTHS when all mom did was cry in her room?".  How do you mourn for the child that you lost & still parent the children that are here?  How does that work?  Do I pretend that all is well?  Or is that wrong too because then they don't learn to deal with their feelings?  Right now, I have no idea what is up & what is down.  So if someone has the magic answer then please let me know because my brain hurts & my heart hurts.