THE SHOT OR NEXPLANON IMPLANT?

I’ve always struggled with being thin I want a birth control that’s going to make me put on weight. I’m almost due to have my baby (37 weeks) and after I give birth to him I want a birth control that is long term. The iud or anything else that goes up there is not an option for me because I’m very prone to infections down there I won’t even use a tampon anymore. Before pregnancy I was barely 90 pounds, now I’m 155 & loving it I have curves and I’m hoping to not lose all of it after birth.