Infant Sexual Abuse

I have already filed a report and am waiting for CPS to come speak with my husband and I so let’s get that out of the way. We believe our 18 month old may be getting molested by my Step Father but don’t want to make false accusations. What are some signs of sexual abuse in infants? Our son has always loved taking baths up until the day my mom told me our son bathed with my stepdad and ever since then he screams bloody murder anytime we even get him near the tub and he has started peeing on us and also grabbing his weewee a lot. I know it’s hard to tell with babies because they obviously aren’t very verbal, but this is not normal for our little boy. We have considered that maybe it is just a phase, but on the 4th of July he did perfectly fine in a swimming pool. What do we need to look for!? Please Help