I do get where you are coming from, often its the jumping from one thing to another that tip us over the edge, ie baby related stuff, v house/refurb stuf fv family and friend stuff v work stuff. Before Dcs it was just work and relationship!
You need to simplify your life to give you more calm,
Online food shopping saves hours and does not have to be more expensive.
Do you need / can you afford a cleaner? 2 hours on a Friday can really help you have a good weekend!
On a Sunday night list all calls that need to be made on Monday morning (or another morning if you work then ) and all errands, try and be efficient about slotting in errands en route.
Occupy toddler with favourite T/v or friend whilst you make calls and knock off your to do list...you can do a lot in an hour.( l used to do this in a soft play corner twice a week with diary and phone to keep on top of work whilst 2 DCs were having fun)
Repeat calls and errand list 3 days later, only do emergencies in between.
Plan seeing family ahead and don't overdo lots of visits unless it is relaxing for you.
List essential jobs divide between you and DH and set times if possible.
Toddlers do not have to go on family trips each weekend they are often easily occupied at home, and this can be less tiring if you are struggling.
Try and leave one weekend day free of household jobs and family commitments. Ask Dh to take over for 3 hours whilst you nap/read or whatever you find relaxing, then swap over.
These are just things that have helped me when my DH was working mostly away, and l was juggling 2 under 2 with no other support and very part time work from home. Hope some of it may help a little.