Welcome to the forum. Cramps between menstrual cycle is known as dysmenorrhea and is considered to be a normal phenomenon experienced by many females. You have not mentioned if it is the first time when you have started spotting after periods or it has been happening to you quite off and on.
Spotting or bleeding after periods is a thing to get concerned about. You should see a gynae, get clinically examined and go through all the investigations needed ( USG, blood/urine examinations,etc ).
The cause of post-menstrual spotting/ bleeding, cramps, pain on sides can be due to many reasons like cysts, fibroids, endometriosis
, ovarian tumors,etc. Get diagnosed and treated well. Take care.