Im so tired of being skinny!

Hello! 
I hope you guys can help me! I'm 26 and 4 months ago I had my baby and during my whole pregnancy I lost so much weight I became so skinny and I had hopes of gaining my weight back but instead I remained skinny probably got worst. And due to that I've become so unhappy and depressed it has affected me sooo much to the point I stopped going out my house because I don't want anyone to see me anymore I'm tired and sad hearing people tell me I'm skinny and stuff like that. All my life I've been in a great shape and been very athletic in my school years and I'm not used to being skinny I'm 5'6 and I'm 103 I used to always be 125-130, I feel so ugly and so sad I can't even look at myself in the mirror like I used to I even asked my partner for some time off because I can't stand him to see me either 😞☹️💔
I really would like some tips on how I can gain weight I just recently started to work out with a few weight but I would like more tips maybe a product that can help me? 
I appreciate all those comment because this is killing me slowly😓