Oh and great news about your DS jabs. So much better when it's over isn't it. I realise now that it's one of those events that you build up in your head! Well, it was for me anyway 
Bella - what crazy lady said that? Ignore ignore ignore! It is so insanely tough with a 3 year old. Absolutely bonkers to suggest that! At age 3 they're going through so much in their little worlds and require a massive amount of patience.
Funny enough today I've been having some time out from my 3 year old son which gave me time to think where we're going wrong. His behaviour is so absolutely embarrassingly appalling it's like I have a new bratty child on board. It's puzzled me because he really loves his baby sister and doesn't show hate towards her. Also, I do make time for him in the day and I do show him lots of love but every day we have very bad behaviour. It's been particularly bad when we've had play dates at our house or at other people's houses. He pushes, says he's bored, says he wants to go home, screams, shouts, snatches... you get the picture. All these things never happened pre baby so I've just been putting the blame on Dd. However, after some thought I've realised it's not Dd. It's what we do that's changed. He misses our energetic life. He's got too much energy that isn't being used and it's turned into anger. It's not my fault but we've spent sooooo many mornings indoors since DD's arrival. I thought having play dates would be enough but it isn't. He misses the walks, the park trips, playing in the garden, soft play, trips to the farm...oh the list is endless!
Anyway, it just clicked today and I'm rather relieved as I can work on fixing it. No more play dates and I'll just have to suggest that friends meet us for walks instead. It's going to mean we miss out on seeing friends I know because they won't want to all meet us so late in the day when they can fit us in but there we go. It will be so worth it as I can't carry on with his bad behaviour. Way too stressful! I need to start suggesting that friends meet us in playgrounds too. It's not the same as going to each others houses as you can hardly talk at parks but it's better then nothing!