What do I do with myself?

Sometimes I just dont know what to do with myself.  I have spent the past 12 years doing everything that I could to make my husband happy, at my own expense.  Now that he has become a lying cheating jackass, I just dont know what to do with myself.  I have never in my life put myself first and it is so fucking strange.  Don't get me wrong, my kids are #1 in my book and always will be, I will do anything to keep them happy.  But when they are with their dad, and I am home left to myself, I just dont know what to do.  My friends say they are always available for me, to spend time with me but they are all happily married with kids of their own so they really dont have much free time.  i have been told to get a hobby.  Not really an easy thing to do since I dont have much money because of him so I try to save it all for my kids.  Went and took a few cake decorating classes, which I always wanted to do, and I really love it and think I am good at it but you cant just make a cake for the hell of it to throw it out.  Make a cake and it should be eaten and the last thing anyone in this house needs is an abundance of sugar.  So even though I love doing it, I need a reason to make one and there just arent many of them.  So then I sit at home, wondering what to do with myself.  How the hell am I supposed to move on if I cant figure out a way to keep busy??