If you got pregnant while breastfeeding, did it affect your supply?

Kailee
I'd like to start TTC in August. My daughter will be 9 months old then. I'd like to breastfeed her for at least a year. 12 months is my goal. I'm just concerned i won't be able to do that if I get pregnant when I hope. I want my kids to be close together in age and I'd like to start trying soon in case it takes a while to conceive my second.