I am in week 22 & have only gained 5 lbs. My midwife is ok with that since she only wants me to gain 20. I am not very much overweight, but she would like to try & keep the baby on the small side to avoid a repeat c/s. Again, I look very pregnant even though I haven't gained so much which makes me feel that all the weight I have gained is going to the right place since most of the extra weight gain just goes towards the mother's fat stores & I don't need any more of those. I don't think a 4 lb gain is something to worry about. Have you had a 20 week ultrasound? I had mine & the baby was right at the size he should be in his development so that made me feel better. Maybe if you haven't had one, you would want to talk with your midwife about having one just to check that the baby is growing at the right pace. It's more the quality of the weight that you gain rather than the quantity I think. Hope that helps.