Help moms! new mommy!?

Im a mommy to an amazing 8 month old son! My problem is not with him, its with my body.The reason I put this on this section is because I normally get good answers from you moms. I gained 21lbs during pregnancy, lost it all within 2 weeks. I guess my metabolism has hit rock bottom or something because I have gained ten pounds!!!! this is unheard of for me, Im only 20 years old. my husband insists I look wonderful but I just cant stand it. I work out and watch what I eat, i also work part time so im always on the move! and with the little one being a speed crawler I never get to sit lol I don't understand how this is happening? moms whats happening to my body? and WHY?! I will take any advice or suggestions. My friend recommends the pills that help cut your cortisol? she swears that they work and since Im not feeding anymore I wouldn't have to worry about harming my son, anyone had any luck with those pills? thanks again!