B737-700
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Situational Awareness; Communication Breakdown; Fatigue
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance
Human Factors
I was exhausted when I walked in the door. I took over R-side in the middle of holding for all DFW and DAL arrivals. A few minutes after taking over; we were told to clear them all back in. I had a string of 5 DAL arrivals and as the first one was 1 minute from approach boundary they called me and told me I was shut off again. I gave all the DAL arrivals a heading and then a fix; FRSTI to hold at. I gave them; in sequence; holding instructions and altitudes to stack them on top of one another: 130; 140; 150; 160 and [I] believe 170 as the altitudes to hold.As the first few entered holding and the back aircraft were entering holding; Approach called and had me bring them back in. I honestly didn't even see that they were descending through each other's altitudes until it was too late. Furthermore; once I saw them flashing it was already too late; there was no way to save it from being a deal so I just did my best to keep them safely separated. None really; better communication between D10 and ZFW TMU would be nice.
ZFW ARTCC Controller reported having numerous losses of separation due to fatigue and not observing the aircraft descend through each other.