you are probably dehydrated. tiredness is one of the sympotoms.
But also, get some b vitamins chewable or sublingual and a good multi vitamin, dont laugh but flintstones with iron are great! and chewable so they get absorbed, and a sublingual b12 pill. that should help alot.
you also have a two year old so you might just have to wait 16 years :D I have a 5 year old, so i know how tiring they are,lol. I had my surgery when DS was almost two and he wore me out!
But really i find if i dont take my B vitamins for a day i get more tired. Oh and also, you should start taking a calcium pill, nothing to do with the ostomy, just this is a good age, try to get a chewable if you can.
Or if you can only find big pills, cut them into pieces so they will be smaller!