Why so lonely?

I am almost a year into being a SAHM and in that time I have had some one with me almost 24 hours a day, 7 days a week.  The result of that is an almost irrational need to be alone.  Unfortunately the few times I have been alone, I've been lonely.  It's hard to believe.  After the kids went to bed the other night, I went out to get them some Valentines Day treats, by myself.  As soon as I got in the car I felt the need to talk to some one.  It was weird.  As much as I long for quiet when the kids are in the car, as soon as the noise is gone, I feel uncomfortable.  

It's taken me a while to realize this, but it's been happening for a while.  I used to think it was just a desire to speak to another adult, but my husband and I talk all the time.  And it's not like I never get to talk to friends on the phone.  When I went to my Uncle's funeral, I thought I felt funny because I missed my kids.  And I did, but I really just felt lonely.

This has been such a mind-boggling revelation... I am afraid to be alone.  I've even gone to having one of the kids sleep with me when my husband is out of town.  I can't sleep without some one with me.  What a weirdo!