It doesn't make any sense that at 169 lbs, "gains were slow" at 5500 Cal/day. At your weight, maintenance intake is somewhere around 2500/day. An intake of 5500/day should be putting on upwards of 6 lbs per week (i.e. from a surplus of 3000 Cal/day).
I think you have one (or more) of the following problems:
1) You're not eating nearly as many calories as you think you are, at least not consistently. As others have mentioned, actually measure your portions and log your intake on a daily basis.
2) You're gaining weight faster than you think you are and you need to keep better track of your weight and weigh yourself more consistently.
3) You actually have a medical condition such as hyperthyroidism, parasites, or a gastrointestinal disorder that inhibits your ability to absorb nutrients.
All that said, it doesn't matter how many calories you're eating if you're not gaining weight. "A lot" doesn't matter if it's still "not enough" to gain weight. Gradually increase your calorie intake until you're gaining 1 lb/wk, or 2 lbs/wk if you want to bulk aggressively. That's a realistic expectation.