Of course it's hard and overwhelming! It's supposed to be, but please know it gets better!
ExH and I separated 18 months ago, when dcs were 4 and 5. What was helpful at those early stages was to focus on the practical stuff. Once that was clear, it was easier to plan/dream/start to work on a vision, and tackle the negative voices in my head.
Of course you need to grieve and mourn your relationship too! That takes time too!
If you are yet to speak to a solicitor, get a consultation booked in.
As for not seeing your children everyday, yes it's tough AND it is a lot more common than we think. Even when married, there were times when I didn't see them for days as I was away on business trips!
And now, I cherish my "me time" more than ever, use the time to connect better with myself & friends, and as a result, I really am a calmer, more fun, more present mama when dcs are with me. It's 9.30am on a Sunday and I'm still in bed...reading! Might even drift off for round two!
As for my dcs, they have gained a dad who now makes plans - takes them swimming, to parks etc. All the things I'd begged him to do so I could get a break when we were together!
My point is, try to consider what the silver lining could be. If you allow yourself to dream more and visualise the positives, you'll have an overall better experienced as you ride the waves.
Hang in there. You're not alone...xx