Hang in there. I had my right total hip replacement done in May of 2018. It took me over a year to even feel like running on it. Even after that, I had some ups and downs. I always was questioning if something was wrong and if I made a mistake getting it done. I experienced the same pain that you are describing and it was crushing. I believe it’s muscular and things are just getting use to being in a new alignment. Lots of stretching, foam rolling, strength exercises really seem to help.
I’ve been feeling really good again, since January. Actually ran a boston qualifier again this august with a 2:59 and sub 17:30 5K. My hip usually tells me when I’m over doing things and I need to listen to it. Lots of hiking up hill, biking, etc.. on days I shouldn’t run.
Keep your head up! Things do get better.