Welcome to the forum! I am the Mississippi Section Coordinator for USPSA, and if I can be of any help, please do not hesitate to send me a PM.cih said:
As for closest clubs, Pearlington mentioned above on the 3rd Sunday of every month should be about the closest as there is no longer a club in Gulfport.
There are matches in Poplarville (http://www.smsps.com/SMPSA.htm) on the 2nd Sunday of every month, and 3-gun matches on other dates (generally 1st Sunday), that should be about 80 miles from you.
Also, the Mobile Practical Shooters (http://mpsa.us/) hold matches on the 2nd and 4th Saturdays near Vinegar Bend, Alabama, which is also probably about 80-90 miles away.