Healthy diet to gain weight

I am 18 years old n about 5'7". I had a baby 8 almost 9 months ago n Im back to the weight I was before I got pregnant.[106pounds] I know many women would be happy to be back the way they were before getting pregnant but I absoultey HATE it
I loved the wieght I gained when I was pregnant n really wouldnt mind being back up to 130-144. I am tired of always being told Im too skinny n need to eat.
I eat but I know I dont eat well like I used to. So Im hoping that someone can help me find a diet that will help me gain weight. Something simple please I cant make a 5 course meal w/ a 8 month old on my hands lol.
So if anyone knows of any diets or even Vitamins supplements I could take that will help me can a healthy weight back so I can feel comfortable in my skin
again please let me know. I would appreicate it soo much!