Shot/injection and abortions

Can you get an abortion while on the shot / injection. I don’t think I’m pregnant but a month before I got my first shot I had sex with a condom ( we were drunk ) and when we finished it wasn’t on but there was cum on the bed ( TMI ). My next period was just spotting and I haven’t had any symptoms also I’m really skinning snd can still suck in all the way. Then I got my injection but I still dont know and I want to have a back up plan. Please help ladies 💗