My weight's been going down - I've lost 4 lbs since Christmas literally without trying, and with not a lot of physical exercise too. Hit a new, semi-worrying low today. Any tips to gain weight?
With a sample size of n=1, it's probably temporary and caused by extra stress; my weight drops by about 10% during exams, but it's also related to my metabolism (pituitary problems). If you're sure it's not it, eat stuff like oats, peanut butter (or peanuts and butter separately), eggs, milk and pasta often and in small portions. Reduce coffee and soda consumption as much as you can. Try adding/substituting some of that swimming and biking with strength exercises, should you prefer to gain some healthy weight instead of plain fat. ;)
That's how I keep my weight above 18 fucking BMI.