I had exactly the same problem at around the same time as you OP! I thought I was being really weird about it so I'm sort of glad to see it's not that uncommon. I substituted my normal toothpaste for the kiddies' one from Superdrug which has a strawberry flavour and that worked really well. I still use it sometimes when I can't face the taste of mint.
I had this never thought it could be the mint, I put it down to the foam triggering my gag reflex which I thought might have been heightened by pregnancy. I just spat more regularly so I didn't get an excessive build up and it worked for me.
But my DD uses strawberry toothpaste, and I think they do other flavours so might be worth looking in the childrens toothpaste section.