the methotrexate shot

So i had the methotrexate shot friday for an ectopic pregancy. My hcg never got that high. The highest was 507. I was told i would have some mild cramping and bleeding. Well i started spotting yesterday on and off but it is very little so i know that is ok. My concern is the cramping. I just dropped to my knees in pain from the cramps. It hit me out of the blue. And im having sharp stabbing vaginal pain. Has this happened to anyone else? The doctor said if it got bad i would need to go to the ER but im just praying it will stop soon. 🤔😣