First, I will say that if you have never been in a shirt before and got it on by yourself, it's not to small, but probably to big. It may be the right size because you can't get it seated properly. The Katana material stretches alot. When I get a new shirt, I cannot get my fingers out to the rings on the first set. By two sets into it, my fingers are out and by the end of the first training session, I'll touch. Every set you do, you will stretch the shirt some. I would not stretch the sleeves yet. If your arms aren't going numb, they're not to tight.
You should NOT be shirt training alone. You have to use extreme weights to get the shirt to work. Just unracking heavier weight can tear up your shoulders. I can't stress enough how important training with experienced shirt lifter is. Both for safety and learning. I'm not sure where Ft Hood is, but I know Mike Womack has a gym in Dallas. Mike's one of the best around. If you want his contact info, I can get it for you. Going it alone can also be very frustrating. Shirt benching has a much different groove than raw benching. You can't raw bench in a shirt. Good luck.
"I can't wait 'til tomorrow, 'cause I get stronger every day!"