How to un-burn out?

I've been burnt out for over half a year and I honestly don't know how to get out of it. I am a single-person architectural firm with occasional help.

Some background:

I really started doing business development for the first time last year since things were slow. Mainly going to events and networking, but also working on my website and overall marketing strategy. I created a lot of promotional material like folders a literature I give to new clients, which I think has had a positive effect. I lost a ton of money with a Facebook ad strategy that went nowhere. Hired professionals to photograph some of my work, since that's one of the most important things I can do from a marketing perspective, and my firm doesn't really have any. Burned through my cash cushion so that's added some stress, especially since I've got two kids in pre-school draining my savings account.

Anywhere, somewhere in the fall I got a bad client who created a construction problem and then wouldn't pay for it. I witheld my work until it was paid and he threatened to sue me, citing a bunch of nonsense like "compensation for taking time off work to deal with XYZ…" He's wealthy so the threat worked, and I had to go through all the insurance and all that. In the end he was bluffing and went away and everything's fine now, but for 3 months I was a wreck.

Work is finally starting to pick up this spring after what was basically an entire year of nearly dead stream of inquiries coming in. But I'm just so TIRED. I could not motivate myself do anything in January or February– from actual work to just doing the dishes at night. Literally just sitting down stressed out of my mind, even though the stress is over. No self-control eating, on the internet all day wasting time instead of doing work.

I was told the stressful winter probably depleted all my vitamins, and after taking some B6 and B12 supplements I felt way better and kind of got out of the slump. But I feel like after the initial perk up I just get easily tired now, like a battery that charges to 25% and stops. I'm pretty much living off coffee despite getting 8+ hours of sleep. Pretty sure living with young kids doesn't help, but I just don't understand how I can wake up with zero energy or motivation to do anything every day.

I'm not sure how to get out of this slump, but assume this has to be common in the entrepreneur community. Has anyone here had experience with this?