Will having sex with a next man that is not my baby father while breastfeeding make my baby take long to walk?

No it won't, but pregnancy can result if you are not using contraception of any kind.

I agree with Dr. Ingram. At the most this is just a myth but it may be a subtle way for the person who told you to comment on the encounter.

Agree with Drs. F and I. If you do not wish to be pregnant, use contraception all the time, every time. Consider implanted contraceptive, or IUD. Practice safe sex. Get HPV vaccine,