What Causes Delayed Periods With Abnormal Abdominal Cramps?

hi when i was 18 (im 23 now) i was pregnant i was in a new relationship and even through i have always wanted children more than anything i knew we both wasnt ready and i had an abortion. now 5 years on im still with the same man and we want to start a family now that we are older. however we have been trying now for 8 months and still no baby. what has me worried through is my period is always late making me get my hopes up each time and im suffer very bad cramps worse that what im used to. my blood type is o rh negative and i dont remember anyone ever saying i needed a shot after the abortion. so now im really worried that i may have destroyed the only chance il ever have at having kids.