Hey RobotPrincess - I know it is hard to have a little one who is not the best at sleeping I just have a couple of suggestions/questions.

Will your DS sleep in the pram? If so then take him for a walk at some stage during the day when you think he is most likely to sleep, or you can even just push the pram back and forth in the house if he is happy with that. I know it can be painful to have to go out each day, but I would often try to time the walk with something I needed to do (go to the shop, mothers group etc). Or if you want some home time, just make sure you stick near home so you can quickly get home once he is asleep, wheel the pram in and have some you time. I would do "loops" around different areas in my suburb. As a bonus all the walking helped me lose weight. You may only need to do it for a short while, till you can get him to settle at home.

Are you breastfeeding? If so you may want to look at your diet. Some bubs are very sensitive to certain foods and food additives. My DD is sensitive to colour 160b, which is found in many cereals, yoghurts, icecreams and custards. So you may even want to look at what he is being fed solids wise. Made a huge difference to us to cut it our of our diet. Google Failsafe for some ideas on what could be a culprit.

Have you tried Brauers Calm. Some people find that it works wonders, others it helps a bit. For us it helps occasionally, so I keep it for the bad times.