I am not sure what you are training for so...:
If you are training to join, keep up the good work. Increase the mileage to about 15-20 miles, then increase the weight and start back at 3-5 miles and work your way up. Don't kill yourself over it if you have time. I am assuming you are going on a hump once a week or more. If you cannot increase the weight anymore, find a really tall hill or a mountain.
If you are training for Afghanistan and are already in the service, drop the pace (or at least don't worry about it as much), increase the weight. Patrols are stupid slow and you will get real good at dropping to a knee in a security posture while waiting for someone to prod at something potentially explosive in the ground. Wearing full PPE, with weapon, ammo, and water your carrying at least 60 pounds on a flak jacket. Also practice casevac as dragging another person really blows.
What I do: I perform 5/3/1 four days a week. I squat 225 (which is 50% of my one rep max) on my non squat day for three sets of five (which will be significantly heavier than any load I will need to carry). Before my bench and press I walk a mile with 80 pounds of weight vest while either doing farmer carry or a sled drag. I have seen great carry over to tactical movements as well as ruck marching. I also will drag a sled for recovery sans weight vest.
Remember that patrol=tactical movement; ruck march=administrative movement (i.e. moving from a relatively non hostile area to another).