Definitely mention it to your GP in case it's some kind of reoccurrence.
Backache isn't unvommon in pregnancy anyway, so if you have any 'weakness' then that might make you more sensitive. When you're pregnant, your body 'relaxes' your joints so it's easy to get aches and pains and pulls. I had backache and hip ache. In my second pregnancy, I also got a kind of sciatica which was very painful for a couple of weeks.
Apart from getting it checked out, all I can suggest is to be very aware of your back and how you're standing, sitting and sleeping. You may find a pregnancy pillow helps a bit with sleeping. I found I couldnt stand too long else my back would be painful, so I made sure I sat often. I also used cushions to support my back.
So you may have a kind of 'double back sensitivity' from your op and from the pregnancy, if you see what I mean. Definitely speak to someone. There are special pregnancy physiotherapists if that would help, plus the midwives may have suggestions too. But because you've had an issue before, just get that checked first.
Hope you feel better soon. Take it very easy XX