Thanks for all the replies. I thought that it was a pretty lame excuse. He is able to run fast and hurdle over fences, climb up trees (fitter than our teen sons!) so his legs are pretty strong.
He spends a lot of time preening lately, shaving before work but will stay stubbly for me which he knows I hate, uses lots of sprays, face creams, eye creams etc. Likes taking selfies etc so he is pretty self absorbed. I suspected he was cheating with or had his eye on someone at work due to that so decided to dig but his location tracker shows only work then home, or gym where we often meet up at to exercise together after work or go together on days off so I doubt he'd try pretending he's there, or doing sport and pub with mates, again I know he is there. See texts from mates arranging it.
I knew about the testosterone surge from working out. It certainly makes me more up for it but not him. I have to ask him for a goodnight kiss, then he turns away from me.
I found out recently that he does watch porn but only very sporadically. Literally once or twice a month on his Internet history then lots of months nothing. Finding that out made me feel more like shit as my body is nothing like a porn actresses and it seems he likes big boobs which I don't have!
I guess he's bored after being with me so long. We have talked about it and he said 'we're not teenagers anymore'
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We were doing it twice a month if that until recently when I wanted to increase it by spicing things up because I needed more intimacy but he just isn't interested.
Not sure how to proceed.