Makena Injections (17P shot)

I went into preterm labor at 22.5 weeks due to incompetent cervix. I lost my son because his lungs were not developed enough to survive. I had a miscarriage a year later. I’m pregnant again and am 18 weeks 3 days. I had a cerclage put in at 13 weeks and started taking the Makena injections (progesterone 17p) at 16 weeks. I’ve had a total of 3 injections. After each injection I have experienced intense pressure in my lower abs/pelvic area and lower back pain. It subsides as the week goes on and almost goes away but then when I get the shot again the following week, it is so intense that it terrifies me. It almost feels like contractions. I’ve been checked and they say everything looks good and my cervix is long. Has anyone experienced this? It’s very troubling for me due to my history. I’m to the point I want to stop taking the injections but I don’t want to have any issues with stopping too early either. Any advice would be greatly appreciated!