Olivia, i had the exact same feelings today. you are not the world's worst mum, the fact that you are looking to baby buddies for help is proof of that!
When I read your post, i could've swapped Lugh's name for Evie. She is EXACTLY the same! when she is awake she smiles sooooo much that people cant believe it when i tell them she is a nightmare to put down for a nap! I never stopped swaddling her although i need to bind her with a rubber band to stop those arms coming out! it drives me nuts! anyways, i think all you can do is to rest when you can - even if that means laying next to them when they are having floor time, or perhaps putting some music on and laying on the bed together. evie loves watching the ceiling fan, it's a good distraction - maybe you have something that could keep lugh occupied while you rest?
i know it's tough and i am just telling myself that it's not forever and that it will get better. just do what you have to do to get through each day - no matter what it is or what anyone else says about it. Enjoy those happy times during the day and when you are trying to put him to sleep, close your eyes, breathe deeply and relax your muscles as much as you can - lugh will feel you relax and it may help.
remember that you're not alone and keep smiling! i'll be thinking of you and sending good vibes!