What’s happening ?

We have been trying to get pregnant for months now. I had my period October 22nd to the 24th. (Usually it’s the 20th-25th) it was Very light. Then I was spotting from the 24th until the 26th. Well the last two days I have been having BAD BAD cramps(worse then my period cramps) in my lower stomach on my left and right side and cramps in my back in the same spots. What is this ??