Is this burn out?

Sounds like burn out to the max. When I was in your shoes, I felt the burnout about 9 months in. Spent the last 3 months of my first year MF A1 job just pretending like the work I was doing took 2-6x longer than it really did (e.g. a 20 min analysis would take me upwards of 2 hours to "wrap up"). That helped keep my "top bucket" rating since I was still ultra-responsive/producing high quality work and secured me a maxed out bonus, and I immediately took a 40% paycut to go work at a no-name lifestyle boutique where I spent the first 4 months really just adjusting back to "normality". 

It sounds like to me you're going to exit soon whether you know it now or not. My advice to you would just be to manage upwards for however long you need until you feel some semblance of control again, and to look at your exit options carefully. It's easy to get blinded by how shitty your current situation is and not carefully choose your next steps as a result ("anything could be better than this"). That personally happened to me--but luckily it worked out as the firm I joined exploded in growth shortly after. But had it not, it would've been something close to a career-ender in high-finance--jumping from an MF to a no-name that stays a no-name. 

Either way, good luck and the best advice I can give you is to work your angles as much as possible in terms of taking control of your time back, whether that's producing a little bit slower or saying "no" more often, and spending the rest of your energy on your next steps since this clearly isn't a sustainable situation to be in.