Well if the letter says, "I strongly recommend this candidate for a post-bacc program" or something similar to that, I am going to say yes, you may have screwed yourself (IMO). I say this because most students do post-bacc's because their application is not strong enough for med school and need to improve it in some way, so an AdCom is going to have no idea in where you stand in that professor's opinion in competitiveness for medical school. They may even see it as the professor not thinking you are competent for med school as they just said they think you need to do a post-bacc.
I feel like if the professor wrote these specifically for post bacc programs, you could be screwed. If they are generic letters, it might be okay, but if you told them you need new letters for med school, they are probably good. -I'm not really sure which it is based on your post.
Maybe an adcom like
LizzyM or Catalyst can chime in here if they have ever seen something similar.