Hi - so sorry to hear about the rash. If it is baby acne, this is a nomral rash that should go away on its own - usually related to hormones from the pregnancy. Typically, we would expect it to be resolving at 4 months, so I wonder if there are other ideas to consider.
Seborrhea is a common cause of bumpy facial rash that can occur on the scalp and eyebrows as yellow, crusty, scaly dandruff and look like red greasy bumps on the cheeks, behind the ears, neck and chest. This too is very common, but there are methods to help it clear faster.