Terrible Twos??? What about Threes???

It's been a trying winter with Luke.  I love the little guy to death but he's been very defiant and difficult lately.  Not to mention the potty training.  I'm pretty sure we've been working on pooping in the potty for over 6 months.  It definitely didn't take a week like some of my friends.  And it's so frustrating, he has no shame nor does he seem to care.  That part has gotten a little bit better, he doesn't need to go every half hour like before.  And with Drew around, that was a nightmare!  But lately he's gotten bad about the backtalking and bossing.  I try to keep some consistency with time-outs but they don't seem to faze him.  Spanking doesn't seem to faze him either.  However, my dad did seem to have an effect on him.  He got onto him yesterday for backtalking my mom.  Mom said he just stood there and wanted to cry but didn't.  Today he was a little sweeter.  He said "no thank you" when I asked if he wanted something to drink.  And he said "thank you for saying thank you."  But he's so hyper too, he's always moving or jumping and I feel like I'm always nagging him to stop doing something. I hate being a nag.  It's got me questioning my parenting skills and praying constantly.  One thing keeps running through my head though, a speech from a woman at a MOPS meeting last year..."I may not be perfect, but I am the perfect parent for my children."