OP - One of the things I'd also try to do is to timeline exactly when you think your marriage started to become "a bit loveless".
People about to embark on an affair engage in a practice which I had never heard about before, but since joining Mumsnet, I have seen it over and over again. They start to withdraw from the marriage, to create a "gap" to allow the affair to happen. My H had been in contact with OW for about 10 months before he actually agreed to have an affair with her. It's all part of the justification process, so that when they finally do start a proper affair, they've managed to reduce their marriage from what it once was.
I have E mails from around the time this all started with my H and I was saying to friends then that I was feeling unsettled and unhappy, but couldn't put my finger on why this was. On the face of it, everything was pretty good, especially my business, which was in a real "up phase". I put it down to autumn blues, a bit of a career crisis (business was great but I wasn't really enjoying work any more), worry about secondary school choices etc. - but absolutely not my relationship with my H.
His withdrawal was pretty subtle, you see.
During the "active phase" of his affair, this withdrawal became much more overt - his behaviour at home was actually appalling, hence me confronting him in the end.
About 2 weeks before I found out, he was monumentally insensitive about a business setback I had endured (unfortunately for me, throughout the affair, my business suffered one setback after another) and at that point, I remember thinking that he wasn't the man for me any longer. So the night I found out, although I wouldn't have described my marriage as loveless, I would have said that were some real problems.
But the real unhappiness started when he tried to make the gap - before that, although we'd had ups and downs, we were actually in a very loving "up" phase. In fact, the last time I remember feeling genuine happiness was exactly the month before OW got in contact with him...
What I'm saying is, don't let your memory play tricks on you. Timeline this and ask yourself some searching questions.