First welcome too PC. Second, I am not sure if anyone here can tell you what to do in that type of situation. Only you will know the answer to that. What I am wondering is, does the coworker know about your Bipolar? Sounds like your husband is saying he would support you through this. I don't know, I am a bit confused because you said he was going too therapy but you told him it wasn't happening??
You have to make this decision. Either concentrate on your marriage and maybe go through counseling together and support one another or tell your hubby how you feel and you want a divorce.
Anyhoot, welcome too PC!