See if you can get to a slingmeet near you - there are a LOT of different brand slings and carriers out there, and different ones work better for different parents and different DCs. Personally I couldn't make an Ergo comfortable, but I get on well with wraps (Hug-a-Bub when DD was little, then a Didymos) and some MeiTais (only got them once DD was > 1yr - BBO and Napsack work for us, MeiTai Baby not so much). Much easier to try before you buy
I got an ergo when dd was about 6 months old, after she got too heavy for me to carry in a baby bjorn, and she lived in it for the next year. But 4 month old ds still can't spread his little legs wide enough to in, and he hates going in cradle style.
I've got a ring sling, but ds always ends up slightly lopsided in it and it kills my shoulder after a while anyway. I just use it in the house if he won' settle.
I've just bought a wrap, and although it is tricky to use at first, it is really comfortable. I practised with a large teddy until I felt confident to put ds in it. There are some grea videos on you tube demonstrating how to use wraps for different carries.
I have a friend that used a BB with her DS. They were both very happy, and she carried him facing forwards a fair amount till he was about 6-9 months. She then tried to start using a Didy wrap, but found his hips were VERY tight and he could not get his legs into the froggy position to make it comfortable and safe.
Whether that's a problem exagerated by being in the BB (the carrying position allows a much straighter hip), because he's a boy, its just the way he is or a combination of all 3 we don't know - but if you know you intend to carry your DC for longer than the BB will allow, you might want to consider using a carrier that encourages a good, flexible hip position from the start.