what is a good way to gain weight?

As long as you're eating enough throughout the day you don't need to force yourself to gain weight. I'm almost 28 weeks into my third pregnancy and I haven't even gained 10 pounds. Just because you aren't gaining weight doesn't mean your baby isn't growing and gaining. If your doctor isn't concerned, there's no need for you to worry. If your doctor is concernd he or she should give you the information you need.