ZFW Controller described a loss of separation event when two aircraft entered holding for DFW at the same altitude. The reporter lists weather; frequency congestion and coordination requirements as casual factors.

Narrative

Aircraft X; an E145 was holding over SPS for delays into DFW at FL330. The airport was not closed but there was a 20 MIT (miles in trail) restriction that we could not meet without holding. Aircraft Y was inbound to SPS to hold; also at FL330. Conflict Alert activated when the aircraft where about 1 1/2 minutes apart. I issued Aircraft X a clearance to expedite to FL320; report reaching FL320. He acknowledged. I then issued Aircraft Y a turn to a 170 heading and traffic. He acknowledged but did not appear to turn. Neither aircraft responded to an RA. I don't know how many aircraft we where working at the time of the event; the sector was fully staffed with R; RA; and Hand-Off. Frequency congestion was very bad. The 20 MIT restriction; coupled with aircraft coming from other corner posts that had shut due to weather made for an impossible situation. When a sector goes crazy; we need to route aircraft; overflights; around the sector. There needs to be better communication with the pilots; there were a lot of questions about weather; delays; etc. This ties up the frequencies. This particular sector has little airspace and is right next to the sector it is feeding; which can be good for sequencing but leaves no room for the hand-off guy and marginalizes his contributions. Also; when we have expanded in-trail; the UKW Sector should not get a stream from SPS and a separate stream from ADM-HI. It's too much coordination to be down the tubes; have someone pointed out; and have to follow or adjust your stream of aircraft because of it.