Sorry about your loss. I can only imagine being a single parent, let alone being a parent myself. I can’t really give you any practical advice based on being a parent, but I can give you some perspective as a child from a pretty much single parent home (not very involved father, so it felt more like a mom + bro combo type family). Please take care of yourself, be the example for your boys. They will learn a lot from how you maneuver through life. If you have any family or other type of support system like friends, don’t be afraid to ask for help.
Please don’t be too hard on yourself, all your boys can really ask from you is to try to do your best. No one is perfect. Life is not perfect. Just keep at it. 🙂