Refusing the breast :-( Period?

12 week old suddenly is so upset every time I try to nurse. As soon as I put her on the side she screams. It has been so frustrating/upsetting for me. I’ve gotten her to latch a few times over the last few days by standing while holding her diagonally across my body and walking around but even then she’s testy (and I can’t make sure she’s latched right since I’m holding her with both arms). She will stay on for 6-7 minutes and then freak out again. She had seemed to be getting distracted recently at the breast and seems to look around while we are walking and nursing. She will take a bottle after these short nursing stints.

Any advice? Is this a nursing strike (if so how do I make it through)? Do I keep offering the bottle or will that make it worse? Could there something wrong that she doesn’t want to be put on her side to nurse or does this happen as they get older?

I had to exclusively pump for my first. I am loving being able to nurse and it’s heartbreaking thinking it could end this soon.

EDIT to add: I just got my first period last night. Anyone have experience with period attributing to difficulties with feeding?