I am new to this forum but thought I would ask for some advice from all of you relating to ADHD.

My partner is ADHD, we have a happy house, similar life goals, similar careers, good friend base, and apparently have crossed bridges that he has never crossed with anyone else. He has previously dated girls and ended things with them after 2 months moving on to the next one. He discussed this with me at length and was adamant that with me we have broken through it. He discussed the future with me, marriage, children, careers, and life. I felt truly special.

As soon as it came to him understanding issues when life got tough, e.g. my grandfather dying, it dawned on me that he is only good at focusing on his issues. He is very self-centered. Whilst I was dealing with that he went away to a wedding and cheated on me with another girl and spent a few days with her. He rang me to tell me what a horrible person I was to try justify his cheating and then dropped the bomb that he had done it. Not only was I dealing with a family member dying but now his infidelity which came unexpectedly as a few days earlier he was telling me how happy he was, how lucky he was to have me etc. His impulsivity and drinking led to him going astray.

He came home and I said that I was not throwing in the towel and we can work through this. He said he wanted to as well. He then spent two weeks only being concerned with his feelings, there was absolutely nothing done to rectify his mistakes and to make me feel better. Again very odd behaviour. He packed up his belongings to leave a few times and I had to stop him and ask him what he was really doing as it was so out of character. One doesnt switch their feelings in a day and he admitted that he feels as if though he is self-destructing.

He went from mood to mood loving me one minute, being unsure the next. We planned a holiday to stay with his family and I decided that when we would return home I would give him space and I asked him to go stay with family for awhile because I could not handle the coldness which I was being presented with after my self-esteem took a shattering. He kept saying it is because he didnt understand himself or love himself for what he did etc. Eventually  I began to see it was all a giant facade. I believe he wants others to love him and is so desperate to get attention that he will do whatever it takes. Even hurting me in the process and having no empathy. He came home and told me all the details of their little affair and how she told him to leave me and he ran with it. He then told me shes not really interesting, he doesnt know why he did it, and that it would only last a few months the way every single other relationship has.

After this he spent 2 days pouring time and energy into me in terms of being affectionate, telling me he loved me etc. We would be cuddled up watching movies and he would thank me for not leaving him or giving up on him. I noticed he was disappearing to the toilet every once in awhile with his laptop and he spent 40 minutes in there at a time. I asked him what he was doing and he said he was planning something special for me. I knew this wasnt right so when I could check I did and found that he was sitting in the toilet downloading porn and stashing it in secret folders on his computer. I didnt understand as I was still having sex with him, never had an issue with porn, we have similar tastes, and the porn kept affecting our sex life as he would get hung up and obsessive over it and then could not focus on me - struggling to keep attention. To keep disappearing claiming he had a bad stomach and was doing something special for me was really hurtful. This was the final straw for me. He is moving out tomorrow.

Has anyone else had a partner that completely went off the rails out of the blue? A partner who cheated, couldnt keep attention or relationships going? I am at a wits end as to what to do as I have tried talking, understanding, being there for him. I am truly in love with this guy despite all of this and havent really focused on the fact that he is a bad human being. We were truly happy prior to all of this in terms of everything working well and he expressed his happiness everyday. For some reason he is doing all that he can to destroy us and to destroy me. He has never made an attempt to help me in all of his.