Help gaining weight

Before being pregnant with my daughter I weighed 125 lbs. After having her I've lost a lot of weight. I once weighed 101lbs at one point and my husband kept calling me anorexic (I wasn't).

I'm trying to get back to my regular weight but its hard for me to put on any pounds. I'm currently 109 and can never get past 110lbs.

Any suggestions or tips on what types of foods to eat to gain some weight would be very helpful.