You don't give much info with regards to what your difficulties in the M have been. What have been her biggest complaints over the years? What changed in April? Was there an arguement? Sounds to me like there may be someone else in the picture giving her the attention that she needs.
Don't think that counseling will change anything for you. It's typically a waste of time and money- the wayward usually just attends to be able to tell friends, family and the kids that she "tried" to save the M. My wife flat out lied to our counsellor for over 9 months, telling her in couples and private sessions that she wasn't in contact with the OM when, in fact, she was.
I recovered my M in a similar situation while living in the same house and sleeping in the same bed- so don't suggest S yet. The best way for her to see your changes is by keeping things as they are for you right now. This will be a long process- take slow, steady, deliberate steps.
