Period

So i was suppose to start my period last month and it never came. I went to the doc when i was 10 days late because i was having a really bad stomach ache. Like Nothing I’ve ever had before. They gave me a pregnancy test and it was negative. (Blood test too) She told me i could be constipated so they gave me stool softeners. She also said if i don’t have a period next month i need to make an apt with my gyno. Well i still haven’t had a period and i was wanting to know if this has ever happened to anyone else before? Did the doc tell you what was wrong?