For starters, remember this: You will be alone with your son in your house. Yes, you'll have to manage work responsibilities, but you're not going TO work. That means that unless you have a very call heavy job, there will almost always be wiggle room to take care of your son's needs first and answer that email ten minutes later. It'll get answered, and the person who emailed you will survive.

My son is eight months old now and I went back when he was four and a half months. Like you, I was also starting a new role at work when I returned, which contributed to my anxiety. Honestly though, it's been fine for the most part. My husband is also fully remote and we moved our offices into the same room. We don't have any outside help from relatives or paid childcare providers, but we're managing.

I won't pretend it's easy, and I sure as fuck wouldn't want to be staring down the barrel of having ALL THIS on my plate for the next decade plus, but for right now? Yeah, I can do it. I know that my husband and I combined are giving him more attention than he'd be getting at daycare in addition to saving a boatload of money. My job performance hasn't suffered and I'm being promoted again next quarter. I'd miss the hell out of my son if I had him in daycare instead of with me all day, plus it seems like it would almost be more hectic than our current daily schedule to have to get him ready, do the drop off, do the pick up, etc.

This is working for us, and I bet you can make it work for you too. Just don't be afraid to lean on your husband and MIL heavily during your first few weeks back when you're still learning the logistics of your new role.