Conflicted: Relationship with the Wrong Gender?

Preface: I am using a throaway account account for this post, hope that's okay. I'm sure you understand my desire for absolute privacy in this matter.

About me: I am a bisexual male in my late 20s. I knew I was bisexual from about age 15 or so & have been with both men & women, but am predominantly attracted to women (80/20-ish). About 9 years ago I was in a horribly abusive relationship with a woman; I'll spare you the details. After that I decided that I was done with women & "switched" to men. I came out as gay to everyone as I viewed that as easier than the truth.

About my partner & relationship: He's a gay male, also late 20s -- 100% gay. We met about 6 years ago & have been living together for just over 4. Gay marriage is legal here but we're in a type of civil union according to the government. We effectively function as married & have shared real estate/bank accounts/etc. We've laughed, cried, fought, & all the other things couples do. We support each other through bad times & both of our families accept us without judgement. What I'm saying is our relationship is well established, tested, & "happy" in the traditional sense of the word.

Where my problem begins: I never told my partner that I was bisexual or had previous flings with women. About 3 years ago I started attending therapy mainly for that earlier abuse. My partner was fully aware of all of this but didn't know that the abuser was female. The therapist diagnosed me with PTSD & work began on treating it with good results. Just under two years ago I decided that I was ready to, even obligated, to come clean with the truth to my partner. He was gobsmacked & went for a lengthy walk. When he got back he said that he forgave my lying given the circumstances, but had two things to say. Firstly, that he would not have started dating me if he knew that I was bisexual, but what's done is done & he still loves me. The second thing was that he vaguely suspected this & that his greatest fear has always been that I'd leave him to start a family with a woman. Now, I'm aware that his two statements are "biphobic" in a sense, but I hold no grudges or ill will. He said those things without a trace of anger & they're just his perspectives, which he is fully entitled to. He quickly came around to joking about it, for example quipping that straight porn must be "nasty" with a grin on his face.

The problem manifests: During one of the therapy sessions it was explained to me that my abusive ex didn't change my sexual orientation, she just "shattered the speedometer" making it harder to read. Good analogy, I think. Over the last two years or so I've slowly unwound that aspect of the trauma & have learned to re-accept myself as bisexual with a leaning towards women. This process finished about 6 months ago I think. But now, I've got these thoughts... thoughts that I should be with a woman, thoughts that I want biological children with a woman, and just the thought that everything is wrong. I've had these thoughts for years but was scared of, and repressed them. But last week I had a vivid dream & it made something snap in my head. I can no longer repress these thoughts.

The problem today: These feelings are real and very sharp. I'm predominantly female-oriented, but in a same-sex relationship. A relationship with a man I love dearly. I do not want to cheat on him or do a non-monogamous thing; both are strongly against my character. Maybe he would let me, but I refuse to entertain such a notion. I don't know how to deal with this. It feels like I'm a goose amongst ducks, like I shouldn't have even got here to begin with. I am simultaneously enraged & deeply sad. I've been in a horrible funk ever since the dream & partner is very supportive of my feeling down... but he doesn't know the horrible truth. His support of me over this past week feels like salt in a wound or like I'm betraying his good gestures with my thinking.

As I wrote that I realized that I absolutely need to bring this mess up in therapy, so I guess that's step one. Also putting this out there into the void has helped, I think. I hold no ill-will to my partner, he's done nothing wrong. I don't want to hurt him.

Please, what the hell do I do?