Totally normal, your body is adjusting to the major change! Your hormones are still trying to balance out, and you are still trying to adjust to a new life and new schedule and new demands. It took 9 months to grow your beautiful baby, so give yourself time to get re-established and back to normal!
(If it makes you feel any better, I just had my 2nd cycle after baby,and it was 7 days long. Then 3 DAYS LATER, I started another period of another 7 days! but Doc assured me all is fine!) Congrats on baby Solomon, and try to get your rest!