Sounds like a couple of things at least are going on: You are not taking enough time for yourself, already mentioned by a couple of good folks on this thread. I know babysitting costs, however, and if you're a single parent sometimes heaps of money aren't just lying under every pillow...maybe a good friend would be willing to pinch hit for a couple hours a week for a few months until you get over this bump in the road.
Also it sounds like if he does not get what he wants he may throw a tantrum and you might be a bit shy about these in public. I am thinking about the shoving into line scene you described - is there something besides having a huge scene which stopped you from correcting him? Maybe you did correct him and you just didn't mention it in your post.
I have had this feeling: if I correct my child they will throw a fit and then the whole thing will just snowball and we'll have to leave, screaming, tears, having to....physically haul your child out of a building, it's all very embarrassing. Like you have no control. But, on the other hand, if you stand there and do not make the correction as needed you really don't have control. Hm. It's a tough balancing act to be sure. I think in the end laying down the rules one more time, perhaps in writing if your son is up to that, and then sticking to them could be helpful.
One other idea, don't know if there are resources like this for you: a parenting class. I am NOT implying you are doing anything but your best, but a class could have these benefits: meeting others with similar issues, taking a bit of that 'time for yourself', they might even provide some childcare while the meeting is going on. Also, a parents' group might work in these same ways - might be hard to find a good fit, but you should consider looking.
Very best of luck to you - sounds like you have a great kid with enormous amounts of curiousity and drive!!
