Period or something else?

Sierra

I had my boy 9 weeks ago via c section and still haven’t had my period. I started having cramps, nausea and pain in my abdomen when I urinate about a week and a half ago. The doctor says is probably my period coming but it’s been a week and a half! His answer was that it will probably be the worst period I’ve ever had. Doesn’t seem right to me. I was also checked for a UTI but that came back okay. Anyone had anything similar. Any advice?