I am so scared that my baby will get cold, but I find it really hard to judge how warm she is and I think I am overdressing her. Now she has this horrible red, blistery rash in the folds of her neck. Could it be heat rash?

Newborn babies are prone to get heat rash easily, so it is likely that is what your baby has. Heat rash is typically a pink or red rash in the folds of the body that are likely to get hot first! Try dressing your baby a little cooler than you have been and see if that makes a difference. Heat rash should fade within a couple of hours if the baby is cooled down, and if she seems uncomfortable then a gentle sponge with tepid water may make her feel better. It is best not to use any type of cream on heat rash, but if it persists then a visit to the doctor is a good idea.