Menstrual Cycle

Hi mummies! I’d like to ask. I gave birth to a still birth baby at 18 weeks a mth ago. My post partum bleeding stopped after 2 weeks of giving birth. Then, 2 weeks later i am having my menses. Is this normal? I do have menstrual cramps but this time round its different. The pain i felt was like the contraction cramps. Is it normal? Have any mummies experienced this before? Should i consult the doctor on this?