I can't blame any of CW's sex partners for not wanting to make their names known given that they would become subject to doxing and threats. CW is likely a sex addict in the same vein of Ross Harris, having indiscriminate sex with any willing partner. Like RH, we will probably discover during trial that his sexual addiction had been escalating in the weeks leading up to the murders.
I think the co-worker will turn out to be female and that it's very possible had become serious about her. So his desire to be with her and not wanting to pay spousal and child support were his primary motives, imo.