I'm trying to adapt my workouts around the big 3 compound movements but my lower back constantly lets me down, I think this is the 3rd or 4th time in the last year this has happened.
People will probably just say MTFU but sometimes you need to find other training methods to reach your goals, at least for the short time while you heal.
I did my back in and basically sacked squats and deadlifts (along with anything else spinal load related, so BORs etc) and had to do other exercises to compensate. Sometimes you just have to.
Being on a cut is never a reason to not push yourself
However, could be your sciatic nerve, I have big issues with mine. Physio is my recommendation, as long as you know a good one. Got any lifts recorded? You should post them up if you haven't already done so.
I had the exact same thing tho, was squatting 120, got a few sets in, and it's like my nerve has moved and is now being forever pinched.
As the monkee says, probably just tweaked something and your back spasmed to save further damage.
See how it is over the next day or two, otherwise just book a private physio session.
Suffice to say I'm going to go easy on squats in the future, if I want to over do it bench press would be a much safer option.
And no

Was you not in a rack or anything? Should have just bailed at the bottom if you had the chance, rather than your bro needing to help