Here are my stats:
M, 5'4", 140lb, 34yo
Calculated BMR 1550, 2000 adjusted for activity

I've been working out 3x/week, fairly sedentary desk work. I started fat loss with 1700-1800 cal/day and got little results. I went down to 1500-1600 cal/day and got even fewer results. Now I've worked my way up to 2500-2600 cal/day for the last few weeks and finally started losing fat (by caliper and mirror, from 18% to 15%). There hasn't been much muscle loss because I'm going up in weights and my body weight has stayed fairly stable at 139-141 lb while the fat's been going down. Can my calculated BMR be that far off? My nutrition tracking is pretty accurate. What body type am I? Anyone else like this? Are there any specific diet/exercise tips for this body/metabolism type? The values seem so wrong that I feel uncomfortable staying at 2600 cal/day even though the measurements say to keep going.

When I bulk, I guess I'll be going to 3000-3600 cal/day which seems excessive for 5'4, 140 lb.

Thanks for your thoughts.