my husband never wants to be intimate and it's wrecking our marriage

When we were dating the sex was great, once we got married it's literally like a light stitch happened and right off the bat we'd have sex only once a week, which turned into every other week, fast forward 4 years later to now and we only have sex once a month, I'm 5 months pregnant with our second baby and we've had sex TWICE-- I've offered to give him blowjobs (which he used to love) hell politely decline and say he's tired or "not in the mood" when we are physical, it's TERRIBLE- it's like he doesn't know what to do with my body, we have sex, missionary, every time. God forbid I try and suggest something new, he actually gets huffy and agitated over it! Over the course of 4 years it has left me feeling undesirable, unwanted, unworthy, it's killed my self esteem entirely. I recently had an affair, a few times he came over to help me paint a room and we got to talking about our lives ect. And we ended up having sex, amazing, incredible, and... it made me hate my husband even more... why didn't he love me that way? Why didn't he want me like that? I have tried sex toys, lingerie, role playing, I know he watches porn and gets off, but I don't measure up to those girls I suppose.. I know he isn't seeing anyone else because he works for my families business... I feel so so guilty about what I've done, I never ever expected I would be in that situation and quite honestly used to judge women or men who went outside the marriage. But I understand it now, I'm not excusing it whatsoever all I'm saying is, I get it, especially for a woman who is vulnerable and hurting and struggles with feeling unwanted by her husband, it's like both times I wasn't thinking, only the rush just kinda take me. It can't happen again, I've blocked this person and I know I need to handle and deal with what's happening in my marriage. Many would argue "just get a divorce if your so unhappy" it's not that simple. I have a house, a child, and another on the way with this man. He's a great person, I don't see that we connect anymore, I want to give it one more year to just try ANYTHING that can save us, without harsh or hurtful words can any of you please tell me some things to try and save my marriage before getting a divorce from my husband and ripping my kids from their home and father?...