What Are The Side Effects Of Methotrexate Injection?

Hi I had Methotrexate injection 2 weeks ago to treat my 3rd ectopic pregnancy. 2 days ago I got unbearable pain in my stomach and back, I could not sit down or stand up straight, Lying down eased it slightly, I went to Hospital but they said my hcg levels had gone down to 600 so nothing was wrong and sent me home with a couple of tramadol, later that night I thought I had wet myself ut it turned out to be a lot of blood. I am worried now because I am still having pain although not as severe, my shoulder is hurting and I have a really bad head ache and keep going dizzy, what do you think is going on?