Potty Training

6 Months in and I'm starting to think what the hell am I doing! We have good days and bad days, but the bad days are like back to square one...

The main reason we started potty training is because my beautifully behaved boy HATED having his nappy changed and it would end in tears, kicks and screaming every time. I tried pull ups but no this child knew what was coming.
I eased him in, I didn't go all military or anything, I usually let him run round half knacked until he got the knack of running to the potty with out the upset of wetting his pants and we would go out in pull ups..he got this quite quickly. BIG mistake I made here! What I should have done is whacked him in the pants first off and let him learn the mistake of 'unhappy pants' (wet pants), I decided to do this 2/3 months down the line instead! And like I said we have good and bad days.
He can be so good when we're out and about and can some times be good when at friends/families houses and I'm so proud that he's dry and there is always lots of praise and high fives. But then when we're at home he seems to slip. Ok I admit the TV is on most of the time but he's not sat glued to it like it's the best thing on earth. We read lots and play and do lots of fun stuff together whilst we're at home and I remind him that the potty is there if he needs a wee and to let me know if he needs to go. Sometimes if he's really engaged in something he's playing with he leaves it a little late, that's fine I can accept this. But for the past 2 days, he hasn't wee'd on the potty/toilet once..NOT ONCE! I've had a bastard cold which has left my patience running low as it is, and I haven't been as entertaining as I try to normally but come on there's no need to punish me child!
He stayed at Lee's mums over the weekend, and as far as I know he's normally quite good at using the toilet there (bar a few accidents when tired etc) I don't know how long she leave's a nappy on after a nap or when he wakes in the morning though. All I know is we were doing really well and now after this weekend it's gone tits up.
Lee's mum came to my rescue yesterday as I was on the verge of a breakdown so she collected Flynn after work. I put him in a pull up as he hadn't had a nap and was falling asleep on me before he left, so I guessed he would fall asleep in the car. How ever when he came home he still had the same pull up on! I didn't have the energy to be pissed off or even mention anything to Lee.
Again this morning he hasn't wee'd once on the potty and has instead decided to pee everywhere else, but he does have the common courtesy to take his wet pants off and put them in his wash bin, thanks mate!

I really don't know, I thought we would have this down by the time the baby comes?! Was I expecting too much from a 2 and a half year old? Am I asking for the world? There is no way I'm giving up because I know he can do it and I have every little faith that he will master it, just a little help along the way maybe?!