I've been paleo since May 2012 but in October 2012 I decided to finally start lifting weights. I'm 5'8" and the most I ever weighed pre-paleo was 155 pounds. When I started lifting weights in October, I weighed 140 pounds. I've steadily gained weight since that time. About 2 weeks ago, I weighed 160 pounds. During this time frame (Oct-Mar), I ate around 2600 calories a day.

Within the past month, I started using whey protein and upped my calories to around 2800 a day. I've been going to the gym pretty consistently 3 days a week (lifting according to a modified version of StrongLifts) but it seems like I've hit a wall. Weighing myself each morning the past 2 weeks, my weight has fluctuated between 158-161 pounds.

Is the obvious answer here to simply eat more? Or is there only so much weight I can gain? Again, I've been thin my whole life and even with a diet of junk food and soda I only maxed out at 155 pounds.