Aw mare, normal lang yan! Maraming moms din na nawalan ng period for months kahit konti lang yung breastfeeding, especially kung exclusive pa rin kaya ng katawan mo despite short BF period, lactational amenorrhea talaga yan. Pero since 17 months na ang baby mo at matagal nang wala ang period, I'd suggest mag-check ka na lang sa OB just to be sure walang other factors, kasi gusto mo ring malaman kung ready na ang body mo for another baby (kung gusto mo pa) or kung may iba pang nangyayari. Hindi ako nag-period talaga until my youngest turned 2, so don't worry pero better safe than sorry, go see your doctor para peace of mind mo!